AVA MCLAREN WAS ridiculously easy to flummox.

Kincaid stretched his arms across the back of the seat as their hired steam cab took them to the vaccination clinic listed on Mr. Thomas's certificate, watching as she tried to pretend what had happened in his rooms hadn't happened. "I think you've read the file several times. Or that particular page, at least."

Big green eyes locked on him, and for a second he tensed, for she looked ready to flee. Perhaps he'd pushed her too far?

The very idea a man might be flirting with you or find you attractive doesn't even occur to you, does it? He didn't even know why he'd said it, but he disliked the idea she saw herself as beneath the notice of a man's attention.

"I'm merely familiarizing myself with the details," she blurted, refusing to take the bait. "I don't want to fail. Not with this case."

"Why is this case so important?"

"It's my first one, working as the lead. I just... I want to be something more than a laboratory assistant. Gemma and Ingrid are—"

"Stop comparing yourself to others," he snapped. "You're you, and you should be proud of that fact. There's a million women like Gemma in the world, thousands of women that can flirt, and seduce, and steal a man's secrets. Not so many with Ingrid's fighting skills, no, but anyone can hit something. But you? There are only a few who have anywhere near your intellect, and even fewer still who retain your sense of empathy."

Ava nibbled at her fingernail. "To feel empathy is easy—"

"In this world? To keep it after seeing so many bloody horrible things.... You have no idea how rare you are. You're the kind of woman who can make a man like me—a man twisted with hate—start to think, maybe he's wrong? Maybe there is goodness in the world? In blue bloods? Maybe there is hope for a lasting peace between humans and cravers?"

"I'll thank you not to use that word, please. I don't like it."

And he was becoming rather helpless against her wishes. "Sorry. I'll try not to... if you promise to stop wishing you were someone else."

"I'll... try." Green eyes danced to him then back to the window. "You're a rather complex man. I sometimes cannot figure you out. When you first started with the Rogues, you were terribly unkind to everybody."

"I was never unkind to you."

"True." She laced her fingers in her lap, her head bowed. "But you've softened toward the others. You barely even snap at Gemma anymore."

"And Gemma doesn't provoke me as much as she used to." He sighed. "Maybe I'm not as big and bad as I pretend to be?"

That earned him a shy smile.

Maybe I am? Because right now, he wanted to be very, very bad, and damn the consequences.

"Maybe," she said, swaying as the carriage pulled up. "But sometimes I think I'm not the only one who pretends to be something they're not?"

The steam cab idled at the curb, and Kincaid glanced out the window. Saved by their arrival. He twitched a brow at her, then opened the door and stepped out. A shadow rippled over them, and he looked up to find a dirigible passing overhead. London was taking to the skies, gathering steam with the rest of Europe. About bloody time. France apparently had fields of airships, and if not for the heavy English dreadnoughts that patrolled the channel, they'd have sent their fleet north a dozen times.

"The vaccination clinic." Ava's gaze slid past him as he helped her down. In the sunlight, her skin seemed creamy and glowing with excitement. "Hopefully we can find some answers here."

He loved the way the thought of an answer to her questions made her flush with life. Only Ava would be practically dancing on her toes at the idea of getting her hands on the vaccine clinics. Kincaid paid the driver, and then headed for the door. "How are we going to play this?"

She withdrew something from within her reticule. "I still have my Nighthawks credentials. They'll have to answer my questions."

"And what do you want me to do?"

"Perhaps try to look broody and menacing," she threw over her shoulder. "It shouldn't be difficult. That's what some of the other Nighthawks do."

Bloody woman. He smiled.

Kincaid tucked the collar up on his shirt. Being intimidating came naturally to him, but sometimes he wished there was something else he could do. He had no book smarts, like Ava did, but when it came to working with his hands and creating a mech device, that was where his talents shone.

Not quite talents required for a spy. Sometimes he wondered what Malloryn had been thinking when the duke had offered him the job.

Ava entered the clinic, the bell above the door tinkling, and there was nothing for it but to follow. The foyer was stark and decorated with painted timber signs advertising what the vaccine did, and carefully printed pamphlets on the small tables. Protect your family from the craving virus. The clinics were government owned, which made people a little wary of them, but with the virus easily transmitted by blood, and no longer a province of the Echelon, it was easier than ever to be infected.

Once upon a time, only aristocratic families were allowed to be made into blue bloods, with each noble son going through the Blood Rites at the age of fifteen to see whether he'd be “worthy” of receiving such an elitist boon. Women had been strictly forbidden from receiving it, which made him wonder about Ava's past, but then accidents occurred.

But where had she come into contact with a blue blood? She was clearly a virgin, so it wasn't as though she'd served as some rich lord's blood thrall. A flash of something hot went through him at the thought—the idea of Ava giving up either her flesh or blood rights to a nobleman in exchange for protection and a rich life made him want to punch something.

"Good afternoon," Ava greeted the receptionist, flashing a small leather badge with a striking hawk embossed upon it in steel. "I'm Miss Ava McLaren of the Nighthawks. I'm here to ask some questions about a crime I'm investigating with my partner, Mr. Kincaid."

The receptionist blanched, her arms half-slung through her cardigan. "A crime? I'm not quite certain how we can help but—"

"Is the clinic doctor on duty?"

"Aye, ma'am. We were both just finishing up for the day. I can see if he's—"

"Tell him we'd like to talk to him," Kincaid interrupted, leaning on the counter and staring at the older woman. "It's official business."

Ava rapped her fingers on the counter as the woman scurried off, and then picked up one of the pamphlets on the vaccine. "Side effects," she read, "include a fever, a rash, sensitivity to light, and a headache. Please see a doctor if symptoms persist beyond a few days."

"No black veins?" It would be too easy.

"No internal bleeding." Ava put the pamphlet back.

The door opened. "This way, sir. Miss. Dr. Harricks has a few minutes to see you." The receptionist ushered them through into the clinic, then raised her voice. "Cheerio, Dr. Harricks. I'll see you tomorrow."

She closed the door behind herself.

The examining room was private and painted a relaxing blue. A gentleman dressed in a tweed suit cleaned his glasses in the corner, his hair neatly combed. "Good afternoon," he said politely, his gaze sweeping over them, then doubling back to Ava with a hint of male appreciation. "I'm Dr. Harricks, the clinic specialist. How may I help you?"

A service automaton swept patiently in the corner, steam hissing from its vents as it worked its way around the room. Needed servicing by the look of it.

"A Mr. David Thomas was a patient of this clinic six weeks ago," Ava started, as Kincaid strolled around the room, glancing at the clean counters and meticulous files. She flipped through her folder. "He was found two days ago, dead in his parlor from internal bleeding and ruptured internal organs. The preliminary autopsy showed he was several weeks into the metamorphosis stage of the craving virus, with CV levels of 12 percent. I wanted to confirm whether Mr. Thomas received a vaccination here."

Dr. Harricks looked surprised, and then he turned to one of his cabinets. "Thomas... Thomas.... It sounds familiar, though I cannot recall a face. I receive dozens of patients through here each day."

"The vaccine is popular?" Kincaid asked, as Harricks flicked through his files and withdrew a slim folder.

"Increasingly," the doctor replied absently. "I'm booked out two months in advance these days. With more and more blue bloods swimming through the general population, people fear for their children."

"The craving virus is becoming more prevalent in the general population?" Ava asked.

"I'm not quite certain whether it's spreading now the legislation against unapproved infections has been lifted," the doctor admitted, "or whether blue bloods have always been there. They were put on a register when the prince consort was in power, and some were hunted and executed, depending upon how they became infected—it was supposed to be restricted to the Echelon, yes? But some slipped beneath notice, and I suspect in the last few years, now the law against casual infection has been changed, they're not hiding as much as they used to. Or at least, they weren't."

"You think that's going to change?" Kincaid frowned.

Harricks seemed to have found the file he wanted. "I expect it will. There's been a push for more vaccinations in the last two or so months, ever since the blood taxes were lowered to two pints per year for each human adult, and the humanists started stirring up trouble again." He hesitated. "It's... well, some of my clients seem angry these days. They're tired of being forced to give their blood so the Echelon can survive. Anti-blue blood sentiment is becoming rife. I thought we'd done away with all that since the revolution, but there's definitely a ripple of dissatisfaction brewing. One only has to look at the recent riots to see that."

"You found it?" Ava gestured toward the file.

"Ah, yes. Mr. David Thomas was vaccinated on the twenty-first. I tested his CV levels beforehand, and his results were conclusive: no factor of the craving virus present in his blood at all. He was 100 percent human when he received his vaccination." The doctor looked at his file again. "That doesn't make sense, unless the brass spectrometer I'm using is uncalibrated. It means the vaccine didn't work, and we've never had anything like that happen before."

Ava went into a line of questioning about how the vaccine was stored, and the science behind it. Kincaid found his attention drifting.

"Do you have a sample of the vaccine?" Ava asked.

There was an icebox in the corner, and the good doctor fetched them a tray of small vials.

"May I?" she asked, gesturing to Dr. Harricks's microscope.

Kincaid nudged the servant drone. It was stuck in the corner, bumping repeatedly against the wall. The sensor must be stuck. "Want me to have a look at your drone unit?" he threw over his shoulder. "I used to work the enclaves."

The doctor waved a hand in his direction with a "Yes, yes," but his attention remained on what Ava was doing.

Kincaid pulled his small lockpick set out of his pocket. There was a three-inch-long screwdriver in there, as well as various other tools. He knelt beside the drone and reached beneath it for the Off switch. It hummed to a stop, an exhale of steam warming his calves. Kincaid placed a hand against the steel barrel body of the drone. Hot. But not excessively so, considering the boiler had been going for a while by the look of it. The bloody things could run on a pint of water a day. He deftly undid the screws in the electrical panel, watching Ava as she reared back from the microscope.

"What is it?" Dr. Harricks demanded of her, drawing Kincaid's attention.

Ava looked perplexed, and adjusted some knob on the microscope. "This batch of vaccine looks like it's been untreated. The virus is alive, not inert."

Harricks pushed her out of the way, pressing his face to the microscope in horror. "That's impossible. I've been meticulous with my testing." He drew back, clearly confused. "You're right."

The good doctor snatched up a vial, reading the labels on it. Kincaid returned to his task, prying the back panel off the servant drone. Wasn't much he could do to help right now. This was Ava's area, not his. And sometimes it didn't hurt to vanish into the background and watch a suspect's body language—not that Harricks was a suspect. Yet.

"Hold on," Harricks burst out, examining the vial she was testing. "This vial label is missing its category number."

Ava leaned closer to look. "Do you think it's been tampered with? Or replaced?"

Kincaid watched for a second, hands setting the panel out of the way as he peered inside.

An 1864 service model. He winced. Jaysus. Didn't the queen provide better funds for her clinics? No wonder the drone was struggling. It was over twenty years old, and he knew from past experience the '64s often had a fault in the wiring of their electrical circuit. He'd fixed enough of them in his first two years at the Southwark Enclave before he transferred to the King Street Enclave, once his talent with mech-work was noticed and he was set to work on war machines.

One of the wires was missing from the circuit board. Without a light, he couldn't see much else, but that was easily the problem. Watching as Ava and the doctor had a spirited discussion about the vaccine's manufacturer, he reached inside and brushed the wire gently out of the way with a wooden tongue depressor he'd found in the doctor's supplies, pausing as he heard a faint click—

Tick, tick, tick....

Kincaid jerked his fingers out of the drone and peered inside. What in the devil's name? There was a small clip attached to one of the wires—a pressure sensor by the look of it. And a luminescent clock face leered up at him from the bowels of the drone, the second hand ticking steadily toward twelve. Anchored to the clock were an explosive device, two sticks of dynamite, and a few wires.

"Ava!" he yelled, launching to his feet and sprinting toward her.

Kincaid caught a startled flash of her expression, the doctor's shocked, "What on earth?" and then he dove toward her and the doctor, sending all three of them flying through the window.

His shoulder hit it first, and glass shattered. They landed in the back alley, sharp shards stabbing into his back. Ava bounced in his arms, and the doctor rolled free, tumbling over the top of him.

"Get down!" he bellowed at Harricks, lurching to his feet with Ava tucked under one arm, throwing them both behind a moveable waste receptacle in the alley.

The doctor held his hands up to protect his head, looking utterly perplexed. "What is the meaning of—"

The explosion lifted him off his feet, flinging him back into the opposite wall. Ava screamed, and Kincaid slammed her into the wall, using his body to protect her from the rubble as bricks, glass, and steel flew past them.

A waft of heat roared over them, thick with black smoke, and his ears rang. Ava squirmed against him, clapping her hands over her ears. It seemed to last forever. But finally, finally the intensity of the heat died down, and Kincaid lifted his head, feeling Ava gasp and collapse against his chest.

The alley was a ruin. The clinic blackened and charred, it's wall half-standing.

Flames crackled. Black smoke spilled from the bowels of the ruined clinic. Kincaid slowly lowered his arm from his face, his bare forearm blistered from the heat, and his head aching where he'd been slammed against the wall. "Harricks?" he yelled.

The doctor was buried beneath a mound of rubble. His boots kicked frantically.

"Ava? Are you unhurt?" Kincaid demanded.

"What?" she asked loudly.

Her acute hearing would have suffered more than his. He cupped her chin, checked her over, finding no trace of injury, before he urged her to stay there and hurried to the doctor's side.

Harricks, mercifully, looked like he'd sustained a broken wrist, and little else other than bruises.

"What happened?" the doctor kept gasping, staring at his burning clinic like a banked fish.

Kincaid helped him to his feet. "Someone planted a bomb inside your service drone. There was a pressure sensor attached to one of the wires, and the second I touched it, I activated the bomb."

"But why?" Ava came out of the shadows, her face sooty and her dress streaked with dirt and burn marks.

He'd never forget how close she'd come to dying. Kincaid glared at the clinic. "Probably to cover their tracks. I think someone tampered with the vaccine vials, replacing some of the vaccine with live samples, from what I could gather. I'd assume the same person planted a bomb in the drone. It had a remote detonation charge upon it, so I'd guess they meant to return one night—or day—and set it off, except I got to it first."

"But why blow up the clinic?" Harricks still looked shocked.

"Why tamper with the vaccine?"

Ava met his gaze, rubbing at the skin in front of her left ear. "It sounds like someone wanted to make people scared of the vaccination clinics."

"Sounds like someone we know," he told her pointedly.

Because both Ulbricht and the dhampir had been trying to cause chaos last month. Maybe this wasn't connected—Ava would demand proof—but he had a gut feeling it was.

* * *

They found the same circumstances at two of the other clinics.

Tampered vials of vaccine. And another automaton drone that smelled like Nobel's blasting powder, according to one Nighthawk. The clinics were cleared and locked down, the Nighthawks sent to examine the remaining four clinics within the city, and a message sent to the Council of Dukes. Reporters lingered at each clinic, shouting questions, but Ava kept her head down and tried not to make eye contact as she directed the Nighthawks to remove the vaccine vials carefully and transport them to Dr. Gibson's lab at the guild.

She found Kincaid carefully removing the back panel of the automaton drone in the alley outside, where he pronounced this particular model to be free of explosive devices. Several Nighthawks breathed sighs of relief, and took it into custody to examine further.

"We're finished here," she finally announced, stepping in front of Kincaid and forcing him to come to an abrupt halt. "Which means it's past time for me to have a look at that arm."

"It's nothing—"

"Don't you give me that nonsense." She gestured to the evacuated clinic. "Sit. And roll up your sleeve!"

To her surprise, Kincaid gave her a wry smile, and then collapsed into a chair. Smoke stained his face, and runnels of sweat had made tracks in it. This only served to highlight the intensity of his eyes. "As you wish."

Ava unwrapped the linen bandages she'd applied earlier, when they'd been in a rush. The sight of his blistered skin made her wince. She'd washed it thoroughly under cold water earlier, and the extent of the damage wasn't too bad. Fairly minimal in fact. But his skin was reddened, and hot to the touch, and there was one blister she didn't like the look of. He'd borne most of the heat wave when the clinic exploded, protecting her with his body.

"This is going to be a little disgusting," she said, spitting into her handkerchief, "but a blue blood's saliva can heal most wounds. Could you please not look?"

He obediently looked away as she pressed her saliva against his skin. "Can't infect me, can it?"

"The craving virus is blood-borne. And I would never risk that if it wasn't." Still, the fact he'd asked bothered her a little.

"I trust you," he muttered, wincing a little.

"Thank you," Ava said quietly, as she used the clinic's bandages to redress his arm once she'd checked it. The redness was already fading, but she hated seeing him hurt like this. "I think you saved my life today."

Kincaid shrugged. "It happened quickly.

Ava slowly looked up from beneath her lashes. "You don't like it when I praise you."

He graced her with another careless smile. "I'm not a hero, angel—"

"I beg to differ," she said, "considering both Dr. Harricks and I most likely owe our lives to your quick thinking."

He had such astonishingly blue eyes. Ava blushed. "Thank you." Straightening out of her crouch, she pressed a swift kiss to his cheek, the smoothness of his freshly shaved skin like silk beneath her lips. "For everything."

Kincaid inhaled slowly, and his fingers caught in her skirts, trapping her. Heat darkened his eyes, and Ava was suddenly aware of how a simple turn of his head might result in her mouth meeting his. She reluctantly lowered her hand from his shoulder and turned away, flushing a little. The kiss had been instinctive. A tender thank-you.

But it wasn't tenderness she saw blazing in the sapphire blue of his eyes. It wasn't tenderness that made his fist clench in her skirts.

"Are you going to let me go?" she whispered, not certain whether she truly wanted him to.

Kincaid looked up from beneath thick black lashes, his fist flexing a little in the fabric of her skirts. "Should I?"

The words stole her breath. She didn't know how to answer him. And maybe he saw it in her face, for he released her, stretching back in his chair and running both hands—human and mech—through his thick, dark hair. "Go, Ava. Give me a minute alone."

"Thank you," she whispered, stepping back out of reach.

She'd thought his flirtations meaningless, and had brushed them aside until now, but as Ava headed for the alley outside to catch her breath, she suddenly realized he wasn't just flirting with her because she was a woman, and that was what Kincaid did. Those heated looks he sent her were specific. The offer he'd made her was centered purely on her. It was Ava he was imagining in his bed in those moments, Ava he visualized whenever he gave her that wicked smile.

And it had been for a while.

"Oh." Ava paused, pressing her back to the wall and sucking in a huge breath. Goodness. Liam Kincaid was flirting with her, Ava McLaren, owner of enough fichus to sink an airship, and the lady most likely to end her days as a spinster, surrounded by a dozen cats.

And he meant every single thing he was silently telling her when their eyes met.

Including his proposition.

* * *

There was no sign of Malloryn when they returned to the safe house, but the woman he'd left in charge in his absence, Isabella Rouchard—or the baroness, as Ava referred to her—was there, and in Malloryn's absence, she was the person they reported to.

"Someone's tampering with the vaccination clinics?" Isabella echoed, once Ava finished giving her report. "I can scarcely believe this. People stricken with the craving virus after receiving a vaccination, this Black Vein, bombs.... What on earth does it all mean?"

Ava exchanged a look with Kincaid. "We have no proof, my lady, but... it has to be connected."

"These riots aren't coming from nowhere," Kincaid added. "I haven't heard much from my mech friends, but the good doctor mentioned unrest among the population. Perhaps that has something to do with it? Maybe someone's got a grudge against the vaccination clinics."

"Or... it could be something more sinister," Ava pointed out.

"You think this has something to do with the dhampir or Ulbricht?" Isabella demanded.

At this Ava hesitated. She wanted the suspect to be their mysterious enemy, but.... "It could be anyone with humanist sympathies who can't forgive the blue bloods, despite the revolution. It might be some of the humanist contingents that were left over from the revolution. It might be the dhampir. We don't know."

Isabella paced the rug in front of Malloryn's ornate desk, her hands clasped behind her back. The woman ran the Rogues in Malloryn's absence, but Ava had had little to do with her in their time together. Gemma could stir the blood in a dead man's veins, but Isabella Rouchard intimidated her on an entirely different level. The baroness was frighteningly beautiful, with sharp black-winged brows, and hair the color of a raven's wings. "I'll mention it to Malloryn. He's busy with his forthcoming wedding at the moment, but I know he'll want word of this. In the meantime...." The woman tapped her ruby lips, staring into the distance. "Keep digging. We need to know who is behind this. If the unrest in the human population grows any worse, it could threaten our peace, and even the crown. We cannot tolerate that."

Ava curtsied politely, and began backing away. "Yes, my lady."

"Ava?" the baroness called.

She paused, her shoulder brushing Kincaid's. "Yes?"

The baroness tipped her head in a polite nod. "You've done very well with this case, but be careful how far you step. Our enemies unleashed vampires on London last month without even a thought to the carnage that might have occurred. If they are the ones behind this, then they won't hesitate to remove you from the situation. If I had the option I'd replace you with Gemma or Charlie, purely because they're more capable of protecting themselves, but they're still not back, so... be careful. "

A chill ran through her.

But Kincaid rested his hand on the small of her back. "If someone wants to hurt Ava, they'll have to go through me first."

And somehow, Ava felt perfectly safe, in a way she hadn't since before Dr. Hague got his hands on her.