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.”