At six o’clock on Wednesday morning, Robin, who had again slept in the spare room, got up and dressed herself in jeans, T-shirt, sweatshirt and trainers. Her backpack contained a dark wig that she had bought online and which had been delivered the previous morning, under the very nose of the skulking journalist. She crept quietly downstairs, so as not to wake Matthew, with whom she had not discussed her plan. She knew perfectly well that he would disapprove.

There was a precarious peace between them, even though dinner on Saturday night with Tom and Sarah had been an awful affair: in fact, precisely because dinner had been so dreadful. It had started inauspiciously because the journalist had indeed followed them up the street. They had succeeded in shaking him off, largely due to Robin’s counter-surveillance training, which had led them to dodge unseen out of a crowded Tube compartment just before the doors closed, leaving Matthew aggravated by what he considered undignified, childish tricks. But even Matthew could not lay the blame for the rest of the evening at Robin’s door.

What had begun as light-hearted analysis over dinner of their failure to win the charity cricket match had turned suddenly nasty and aggressive. Tom had suddenly lashed out drunkenly at Matthew, telling him he was not half as good as he thought he was, that his arrogance had grated on the rest of the team, that, indeed, he was not popular in the office, that he put people’s backs up, rubbed them the wrong way. Rocked by the sudden attack, Matthew had tried to ask what he had done wrong at work, but Tom, so drunk that Robin thought he must have started on the wine long before their arrival, had taken Matthew’s hurt incredulity as provocation.

“Don’t play the fucking innocent with me!” he had shouted. “I’m not going to stand for it any more! Belittling me and fucking needling me—”

“Was I?” Matthew asked Robin, shaken, as they walked back towards the Tube in the darkness.

“No,” said Robin, honestly. “You didn’t say anything nasty to him at all.”

She added “tonight” only in her head. It was a relief to be taking a hurt and bewildered Matthew home, rather than the man she usually lived with, and her sympathy and support had won her a couple of days’ ceasefire at home. Robin was not about to jeopardize their truce by telling Matthew what she was planning this morning to throw the still-lurking journalist off her trail. She couldn’t afford to be followed to a meeting with a forensic pathologist, especially as Oliver, according to Vanessa, had needed a great deal of persuasion to meet Strike and Robin in the first place.

Letting herself out quietly of the French windows into the courtyard behind the house, Robin used one of the garden chairs to clamber onto the top of the wall that divided their garden from that of the house directly behind them, of which the curtains were, mercifully, closed. With a muffled, earthy thud, she slid off the wall onto the neighbors’ lawn.

The next part of her escape was a little trickier. She had first to drag a heavy ornamental bench in their neighbor’s garden several feet, until it stood plumb with the fence, then, balancing on the back of it, she climbed over the top of the creosoted panel, which swayed precariously as she dropped down into a flowerbed on the other side, where she staggered and fell. Scrambling up again, she hurried across the new lawn to the opposite fence, in which there was a door to the car park on the other side.

To Robin’s relief, the bolt opened easily. As she pulled the garden gate closed behind her, she thought ruefully of the footprints she had just left across the dewy lawns. If the neighbors woke early, it would be only too easy to discover whence had come the intruder who had invaded their gardens, shifted their garden furniture and squashed their begonias. Chiswell’s killer, if killer there was, had been far more adept at covering their tracks.

Crouching down behind a parked Skoda in the deserted car park that served the garage-less street, Robin used the wing mirror to adjust the dark wig she had taken out of her backpack, then walked off briskly along the street that ran parallel with Albury Street, until she turned right into Deptford High Street.

Other than a couple of vans making early morning deliveries and the proprietor of a newsagent raising the metal security roller door from his shop front, there was hardly anybody around. Glancing over her shoulder, Robin felt a sudden rush, not of panic, but of elation: nobody was following her. Even so, she didn’t remove her wig until she was safely on the Tube, giving the young man who had been eyeing her covertly over his Kindle something of a surprise.

Strike had chosen the Corner Café on Lambeth Road for its proximity to the forensics laboratory where Oliver Bargate worked. When Robin arrived, she found Strike standing outside, smoking. His gaze fell to the muddy knees of her jeans.

“Rough landing in a flowerbed,” she explained, as she came within earshot. “That journalist is still hanging around.”

“Matthew give you a leg up?”

“No, I used garden furniture.”

Strike ground out his cigarette on the wall beside him and followed her into the café, which smelled pleasantly of frying food. In Strike’s opinion, Robin looked paler and thinner than usual, but her manner was cheerful as she ordered coffee and two bacon rolls.

“One,” Strike corrected her. “One,” he repeated regretfully to the man behind the counter. “Trying to lose weight,” he told Robin, as they took a recently vacated table. “Better for my leg.”

“Ah,” said Robin. “Right.”

As he took a seat at a recently vacated table and swept crumbs from it with his sleeve, Strike reflected, not for the first time, that Robin was the only woman he had ever met who had shown no interest in improving him. He knew that he could have changed his mind now and ordered five bacon rolls, and she would simply have grinned and handed them over. This thought made him feel particularly affectionate towards her as she joined him at the table in her muddy jeans.

“Everything OK?” he asked, salivating as he watched her put ketchup on her roll.

“Yes,” lied Robin, “all good. How is your leg?”

“Better than it was. What does this bloke we’re meeting look like?”

“Tall, black, glasses,” said Robin thickly, through a mouthful of bread and bacon. Her early morning activity had made her hungrier than she had been in days.

“Vanessa back on Olympics duty?”

“Yeah,” said Robin. “She’s badgered Oliver into meeting us. I don’t think he was that keen, but she’s after promotion.”

“Dirt on Ian Nash will definitely help,” said Strike. “From what Shanker told me, the Met’s been trying—”

“I think this is him,” whispered Robin.

Strike turned to see a lanky, worried-looking black man in rimless glasses standing in the doorway. He was holding a briefcase. Strike raised a hand in greeting and Robin slid her sandwich and coffee over to the next seat, to allow Oliver to sit opposite Strike.

Robin was not sure what she had expected: he was handsome, with his high-rise hairstyle and pristine white shirt, but seemed suspicious and disapproving, neither of which trait she associated with Vanessa. Nevertheless, he shook the hand Strike proffered and, turning to Robin, said:

“You’re Robin? We’ve always missed each other.”

“Yes,” said Robin, shaking hands, too. Oliver’s spotless appearance was making her feel self-conscious about her disheveled hair and muddy jeans. “Nice to meet you, at last. It’s counter service, shall I get you a tea or coffee?”

“Er—coffee, yeah, that’d be good,” said Oliver. “Thanks.”

As Robin went to the counter, Oliver turned back to Strike.

“Vanessa says you’ve got some information for her.”

“Might have,” said Strike. “It all depends on what you’ve got for us, Oliver.”

“I’d like to know exactly what you’re offering before we take this any further.”

Strike drew an envelope out of his jacket pocket and held it up.

“A car registration number and a hand-drawn map.”

Apparently this meant something to Oliver.

“Can I ask where you got this?”

“You can ask,” said Strike cheerfully, “but that information’s not included in the deal. Eric Wardle will tell you my contact’s got a record of hundred percent reliability, though.”

A group of workmen entered the café, talking loudly.

“This’ll all be off the record,” said Strike quietly. “No one’ll ever know you talked to us.”

Oliver sighed, then bent down, opened his briefcase and extracted a large notebook. As Robin returned with a mug of coffee for Oliver and sat back down at the table, Strike readied himself to make notes.

“I’ve spoken to one of the guys on the team who did forensics,” Oliver said, glancing at the workmen who were now bantering loudly at the next table, “and Vanessa’s had a word with someone who knows where the wider investigation’s going.” He addressed Robin. “They don’t know Vanessa is friendly with you. If it gets out that we helped—”

“They won’t hear it from us,” Robin assured him.

Frowning slightly, Oliver opened his notebook and consulted the details he had jotted there in a small but legible hand.

“Well, forensics are fairly clear-cut. I don’t know how much technical detail you want—”

“Minimal,” said Strike. “Give us the highlights.”

“Chiswell had ingested around 500mg of amitriptyline, dissolved in orange juice, on an empty stomach.”

“That’s a sizable dose, isn’t it?” asked Strike.

“It could have been fatal on its own, even without the helium, but it wouldn’t have been as quick. On the other hand, he had heart disease, which would have made him more susceptible. Amitriptyline causes dysrhythmia and cardiac arrest in overdose.”

“Popular suicide method?”

“Yeah,” said Oliver, “but it’s not always as painless as people hope. Most of it was still in his stomach. Very small traces in the duodenum. Suffocation is what actually killed him, on analysis of the lung and brain tissue. Presumably the amitriptyline was a back-up.”

“Prints on the glass and the orange juice carton?”

Oliver turned a page in his notebook.

“The glass only had Chiswell’s prints on it. They found the carton in the bin, empty, also with Chiswell’s prints on, and others. Nothing suspicious. Just as you’d expect if it had been handled during purchase. Juice inside tested negative for drugs. The drugs went directly into the glass.”

“The helium canister?”

“That had Chiswell’s prints on it, and some others. Nothing suspicious. Same as the juice carton, like it had been handled during purchase.”

“Does amitriptyline have a taste?” asked Robin.

“Yeah, it’s bitter,” said Oliver.

“Olfactory dysfunction,” Strike reminded Robin. “After the head injury. He might not have tasted it.”

“Would it have made him groggy?” Robin asked Oliver.

“Probably, especially if he wasn’t used to taking it, but people can have unexpected reactions. He might’ve become agitated.”

“Any sign of how or where the pills were crushed up?” asked Strike.

“In the kitchen. There were traces of powder found on the pestle and mortar there.”

“Prints?”

“His.”

“D’you know whether they tested the homeopathic pills?” asked Robin.

“The what?” said Oliver.

“There was a tube of homeopathic pills on the floor. I trod on them,” Robin explained. “Lachesis.”

“I don’t know anything about them,” said Oliver, and Robin felt a little foolish for mentioning them.

“There was a mark on the back of his left hand.”

“Yes,” said Oliver, turning back to his notes. “Abrasions to face and a small mark on the hand.”

“On the face, too?” said Robin, freezing with her sandwich in her hand.

“Yes,” said Oliver.

“Any explanation?” asked Strike.

“You’re wondering whether the bag was forced over his head,” said Oliver; it was a statement, not a question. “So did MI5. They know he didn’t make the marks himself. Nothing under his own nails. On the other hand, there was no bruising to the body to show force, nothing disarranged in the room, no signs of a struggle—”

“Other than the bent sword,” said Strike.

“I keep forgetting you were there,” said Oliver. “You know all this.”

“Marks on the sword?”

“It had been cleaned recently, but Chiswell’s prints were on the handle.”

“What time of death are we looking at?”

“Between 6 and 7 a.m.,” said Oliver.

“But he was fully dressed,” mused Robin.

“From what I’ve heard about him, he was quite literally the kind of bloke who wouldn’t have been caught dead in pajamas,” said Oliver drily.

“Met’s inclining to suicide, then?” asked Strike.

“Off the record, I think an open verdict is quite likely. There are a few discrepancies that need explaining. You know about the open front door, of course. It’s warped. It won’t close unless you shut it with force, but it sometimes jumps back open again if you slam it too hard. So it could have been accidental, the fact that it was open. Chiswell might not have realized he’d left it ajar, but equally, a killer might not have known the trick to closing it.”

“You don’t happen to know how many keys to the door there were?” asked Strike.

“No,” said Oliver. “As I’m sure you’ll appreciate, Van and I had to sound only casually interested, asking all these questions.”

“He’s a dead government minister,” said Strike. “Surely you didn’t have to sound too casual?”

“I know one thing,” said Oliver. “He had plenty of reasons to kill himself.”

“Such as?” inquired Strike, pen poised over his notebook.

“His wife was leaving him—”

“Allegedly,” said Strike, writing.

“—they’d lost a baby, his eldest son died in Iraq, the family say he was acting strangely, drinking heavily and so on, and he had serious money problems.”

“Yeah?” said Strike. “Like what?”

“He was almost wiped out in the 2008 crash,” said Oliver. “And then there was… well, that business you two were investigating.”

“D’you know where the blackmailers were, at the time of—?”

Oliver made a swift, convulsive movement that nearly knocked over his coffee. Leaned towards Strike he hissed:

“There’s a super-injunction out, in case you haven’t—”

“Yeah, we’ve heard,” said Strike.

“Well, I happen to like my job.”

“OK,” said Strike, unperturbed, but lowering his voice. “I’ll rephrase my question. Have they looked into the movements of Geraint Winn and Jimmy—?”

“Yes,” said Oliver curtly, “and both have alibis.”

“What are they?”

“The former was in Bermondsey with—”

“Not Della?” blurted Robin, before she could stop herself. The idea of his blind wife being Geraint’s alibi had struck her, somehow, as indecent. She had formed the impression, whether naively or not, that Della stood apart from Geraint’s criminal activity.

“No,” said Oliver tersely, “and do we have to use names?”

“Who, then?” asked Strike.

“Some employee. He claims he was with the employee and the bloke confirmed it.”

“Were there other witnesses?”

“I don’t know,” said Oliver, with a trace of frustration. “I assume so. They’re happy with the alibi.”

“What about Ji—the other man?”

“He was in East Ham with his girlfriend.”

“Was he?” said Strike, making a note of it. “I saw him being marched off to a police van, the night before Chiswell died.”

“He was let off with a caution. But,” Oliver said quietly, “blackmailers don’t generally kill their victims, do they?”

“Not if they’re getting money out of them,” said Strike, still writing. “But Knight wasn’t.”

Oliver looked at his watch.

“Couple more things,” said Strike equably, his elbow still planted on the envelope containing Ian Nash’s details. “Does Vanessa know anything about a phone call to his son that Chiswell made on the morning of his death?”

“Yeah, she said something about that,” said Oliver, flicking backwards and forwards through his notebook to find the information. “Yeah, he made two calls just after 6 a.m. First to his wife, then to his son.”

Strike and Robin looked at each other again.

“We knew about the call to Raphael. He called his wife as well?”

“Yeah, he called her first.”

Oliver seemed to read their reaction correctly, because he said:

“The wife’s totally in the clear. She was the first person they investigated, once they were satisfied it wasn’t politically motivated, obviously.

“A neighbor saw her go into the house on Ebury Street the evening before and come out shortly afterwards with a bag, two hours before her husband came back. A taxi driver picked her up halfway down the street and took her to Paddington. She was caught on camera on the train back to wherever she lives—is it Oxfordshire?—and apparently there was someone at the house when she got home, who can vouch for the fact that she arrived there before midnight and never left again until the police came round to tell her Chiswell was dead. Multiple witnesses to her whole journey.”

“Who was at the house with her?”

“That, I don’t know.” Oliver’s eyes moved to the envelope still lying beneath Strike’s elbow. “And that really is everything I’ve got.”

Strike had asked everything he had wanted to know, and had gained a couple of bits of information he had not expected, including the abrasions to Chiswell’s face, his poor finances and the phone call to Kinvara in the early morning.

“You’ve been a big help,” he told Oliver, sliding the envelope across the table. “Much appreciated.”

Oliver appeared relieved that the encounter was over. He stood up and, with one more hasty handshake and a nod to Robin, departed the café. Once Oliver had stridden out of sight, Robin sat back in her chair and sighed.

“What’s that glum expression for?” asked Strike, draining his mug of tea.

“This is going to be the shortest job on record. Izzy wants us to prove it was Kinvara.”

“She wants the truth about her father’s death,” said Strike, but he grinned at Robin’s skeptical expression, “and, yeah, she’s hoping it was Kinvara. Well, we’ll have to see whether we can break all those alibis, won’t we? I’m going to Woolstone on Saturday. Izzy’s invited me over to Chiswell House, so I can meet her sister. Are you in? I’d rather not drive, the state my leg’s in at the moment.”

“Yes, of course,” said Robin immediately.

The idea of getting out of London with Strike, even for a day, was so appealing that she did not bother to consider whether she and Matthew had plans, but surely, in the glow of their unexpected rapprochement, he would raise no difficulties. After all, she had not worked for a week and a half. “We can take the Land Rover. It’ll be better on country roads than your BMW.”

“You might need diversionary tactics if that hack’s still watching you,” said Strike.

“I think I could probably throw them off more easily in a car than on foot.”

“Yeah, you probably could,” said Strike.

Robin was in possession of an advanced driving qualification. Though he had never told her so, Robin was the only person by whom he would willingly be driven.

“What time are we supposed to be at Chiswell House?”

“Eleven,” said Strike, “but plan to be away for the whole day. I fancy taking a look at the Knights’ old place while we’re there.” He hesitated. “I can’t remember whether I told you… I kept Barclay undercover with Jimmy and Flick.”

He was braced for annoyance that he had not discussed it with her, resentment that Barclay had been working when she wasn’t, or, perhaps most justifiably, a demand to know what he was playing at, given the state of the agency’s finances, but she simply said, with more amusement than rancor:

“You know you didn’t tell me. Why did you keep him there?”

“Because I’ve got a gut feeling there’s a lot more to the Knight brothers than meets the eye.”

“You always tell me to mistrust gut feelings.”

“Never claimed not to be a hypocrite, though. And brace yourself,” Strike added, as they got up from the table, “Raphael’s not happy with you.”

“Why not?”

“Izzy says he fell for you. Quite upset you turned out to be an undercover detective.”

“Oh,” said Robin. A faint pink blush spread over her face. “Well, I’m sure he’ll bounce back fast enough. He’s that type.”