Julia peered into the small infirmary room in amazement. Violet was perched on the edge of an infirmary bed with the two young girls from Crossness, detangling their hair in long, strokes with a wide-toothed comb before plaiting it close to their heads.

Around twenty surviving scavengers had been brought to the safety of the CB after the Chittrix attack. The two girls sat cross-legged, rifling through a basket of hair ribbons that Violet had conjured up from somewhere. Neither spoke, but their shoulders had dropped the hunched, frightened tension they’d had when they arrived at the CB. Their faces were animated and pink as they threaded Violet’s long auburn locks through their own small fingers.

Julia was drawn to the girls. The youngest was about the same age Maria had been when she’d died. After leaving Sawyer that morning, she’d headed to the infirmary, ostensibly to check on the girls, but primarily to soothe her own curiosity.

But Violet had beaten her to it, and Julia hesitated behind the glass of the nurse’s station when she saw the small group in front of her. Violet looked softer, her rough edges tucked away while she spoke with the girls. There were no weapons strapped to her body. That had to be a first.

Julia turned to leave, happy they were safe, and walked straight into Nathan Darr. She collided with the unyielding wall of his chest and bounced off his muscled body.

“Hey.” He raised his hands in surprise but didn’t step back. Julia retreated, wary of his motives.

“How long have you been standing there?” Just because he’d been welcomed into the safety of the CB didn’t mean she trusted him at all.

Darr’s expression was cool and guarded, his midnight-blue eyes keeping secrets behind an unkempt fringe. He peered through the nurse’s screen and smiled. “I came down to check on the girls.”

Julia followed the direction of his sight and softened. “Me too. V’s taking good care of them.”

“I see that. Garrick’s sister?”

The casual tone of his voice clashed with the close attention he was paying to V.

“Yes.”

He gave the smallest of nods, his expression giving nothing away.

Julia squeezed past him, her back to the wall. He was tall and lean, with a dirty, angular swarthiness that she found disquieting. She stepped back out into the main corridor, releasing a tiny sigh of relief before she realized that Darr, like a dark shadow, was tailing her.

“Can I help you?” she asked, struggling to keep the irritation from her voice. She’d done the small talk, and she wasn’t even very fluent at that. Julia increased the length of her stride, but Darr kept up with her, his legs effortlessly matching her pace. She’d have to jog if she wanted to lose him.

His voice was smooth, catching her off-guard. “Rumor has it you worked for the government in weapons development. That you made the device that took out the primary hive?”

Julia gave a short, derisory snort. “You shouldn’t believe everything you hear.”

“Impressive for a woman.”

What!

They were passing a couple deep in conversation so Julia waited till they were out of earshot. Then she halted abruptly and spun toward Darr, her patience dwindling on a thin thread.

“Can I help you, or are you just tagging along to insult me?”

He gave her a benevolent, lopsided smile, his demeanor casually assessing. “I was just making conversation.”

“Making conversation?” Her tone was caustic even to her own ears.

He watched her with a slow burn of nonchalance. “If I’m bothering you I apologize. It wasn’t intended.” He dipped his head in a conciliatory gesture, but his scrutiny was impenetrable, setting her nerves on edge.

She gave a dismissive shake of her head and spun on her heel. She was only a minute from her lab. She’d get rid of him there.

“Did you know they knew each other?” His voice was impassive, but close to her shoulder. God, he was still following her. The man was so quiet.

Julia squashed a sting of anger. She could play games, if that’s what he wanted. “I have no idea what you’re talking about.”

“Yes, you do. Beth and your friend, Sawyer.”

She bit her lower lip, keeping her voice measured. “That’s old news. Tell me something I don’t know.”

“Ah, if you already knew they were together then I’m wasting my time. Beth spoke about him. He made quite an impression. Before, you know, the invasion.”

Julia breathed in sharply. Together?

Sawyer’s words echoed in her head. He’d been working. Beth had been his target. He hadn’t mentioned being in a relationship with her. Understanding dawned as everything clicked into place. The expression on Sawyer’s face. How upset he’d been. Her stomach cramped.

Darr continued, his dark eyes absorbing everything. “Sawyer must be devastated. To lose a lover, to watch her die like that…well.”

Julia glanced away. Her face stung, raw and exposed. Her heart raced, and her lips parted as she fought to hold it together. She halted at her lab door. Lovers. Sawyer had kept the truth from her. Betrayal stung, forcing her to close her eyes for a second. But then, maybe I gave him no other option by holding him at a distance?

She composed herself, locking her emotions under wraps in the consummately skilled way she always did. She fished a key from her pocket, the snick of the oiled lock clicking under her hands. “I have to go now.”

An inscrutable smile twitched the corner of Darr’s lip. He leaned on the doorframe. “I’d like to see what you have in here.”

“We both know that’s not going to happen.”

He scanned the empty corridor around them. “No one’s around. I won’t tell. Besides, aren’t we in this together now?”

Julia’s hand twitched to slap the shadow of beard on his cheek.

“I might be of use.”

Julia raised her eyebrows.

He held his hands up. “Seriously.”

She blinked, scrutinizing his raw-boned face as she bit the inside of her lip. “How?”

“In the last couple of months, the water supply for our hydroponic beds became opaque with organic sediment. It’s more like soup.”

Julia stared at him, waiting. She thought about the green, shimmering algae that had covered Sawyer’s body when he’d climbed out of the water after fixing the coolant system, but she remained silent. He was going to have to do better.

Darr contemplated her scowl. “You’re hard work.” A broad smile finally graced his face. He was a different man when he smiled. He kept talking. “The water temperature in the tunnels around Crossness has risen by several degrees.”

Her thoughts connected. Wading through the sewers to get Crossness. Fingers trailing in the lukewarm water, noticing it but not understanding the implications.

“The density of alien plant life in the sewers has also increased in the last few months, faster than you would expect from natural colonization. It’s more like the area has been seeded. Some of the plants have demonstrable properties of thermogenesis.”

“Thermogenesis?” She failed miserably to keep her voice casual as he folded his arms now that he knew he had her attention.

“Yes. The plants generate heat to raise the temperature of their environment to what they prefer, in this case, by a few degrees. Some Earth algae have benefited too, preferring the increasingly Mediterranean temperatures of parts of the London Sewer system.”

Julia’s pulse quickened. She pushed her anger at Sawyer to the back of her mind. There was no point in pretending anymore. “And?”

“If alien vegetation prefers warm water, maybe the Chittrix and Scutters do too? Warm, sediment-rich water for them to swoop through unseen. What’s not to like?” He hesitated, sizing her up. “The thermogenic plants aren’t a coincidence. I’m making an educated guess that it’s colder in the sewer system than it would have been in the primary hive. Even Earth insects need warmth to aid incubation of larvae and eggs. I haven’t got the equipment to examine the composition of the water but I’m guessing the algae may infuse it with proteins. Proteins that might nourish alien eggs and larvae.”

She gave him a long, slow look. They were at an impasse with the Chittrix. Nobody knew where the aliens were nesting and they needed all the help they could muster. If they didn’t start working together as humans and fighting the Chittrix instead of each other, they might as well give up now.

Darr pre-empted her, placing his hand on the door handle, his expression questioning. “Shall we?”