The houses in Alma Grove were narrow and Strike could well imagine loud noises traveling easily through the walls. Giving Mallik what he judged to be sufficient time to remove his jacket and shoes, Strike approached the turquoise door and knocked.

After a few seconds’ wait, Aamir opened up. His expression changed from pleasant inquiry to shock. Aamir evidently knew exactly who Strike was.

“Aamir Mallik?”

The younger man did not speak at first, but stood frozen with one hand on the door, the other on the hall wall, looking at Strike with dark eyes shrunken by the thickness of the lenses in his glasses.

“What do you want?”

“A chat,” said Strike.

“Why? What for?”

“Jasper Chiswell’s family have hired me. They aren’t sure he committed suicide.”

Appearing temporarily paralyzed, Aamir neither moved nor spoke. Finally, he stood back from the door.

“All right, come in.”

In Aamir’s position, Strike too would have wanted to know what the detective knew or suspected, rather than wondering through fretful nights why he had called. Strike entered and wiped his feet on the doormat.

The house was larger inside than it had appeared outside. Aamir led Strike through a door on the left into a sitting room. The décor was, very obviously, the taste of a person far older than Aamir. A thick, patterned carpet of swirling pinks and greens, a number of chintz-covered chairs, a wooden coffee table with a lace cloth laid over it and an ornamental edged mirror over the mantelpiece all spoke of geriatric occupants, while an ugly electric heater had been installed in the wrought iron fireplace. Shelves were bare, surfaces denuded of ornaments or other objects. A Stieg Larsson paperback lay on the arm of a chair.

Aamir turned to face Strike, hands in the pockets of his jeans.

“You’re Cormoran Strike,” he said.

“That’s right.”

“It was your partner who was pretending to be Venetia, at the Commons.”

“Right again.”

“What d’you want?” Aamir asked, for the second time.

“To ask you a few questions.”

“About what?”

“OK if I sit down?” asked Strike, doing so without waiting for permission. He noticed Aamir’s eyes drop to his leg, and stretched out the prosthesis ostentatiously, so that a glint of the metal ankle could be seen above his sock. To a man so considerate of Della’s disability, this might be sufficient reason not to ask Strike to get up again. “As I said, the family doesn’t think Jasper Chiswell killed himself.”

“You think I had something to do with his death?” asked Aamir, trying for incredulity and succeeding only in sounding scared.

“No,” said Strike, “but if you want to blurt out a confession, feel free. It’ll save me a lot of work.”

Aamir didn’t smile.

“The only thing I know about you, Aamir,” said Strike, “is that you were helping Geraint Winn blackmail Chiswell.”

“I wasn’t,” said Aamir at once.

It was the automatic, ill-considered denial of a panicked man.

“You weren’t trying to get hold of incriminating photographs to use against him?”

“I don’t know what you’re talking about.”

“The press are trying to break your bosses’ super-injunction. Once the blackmail’s out in the public domain, your part in it won’t remain hidden for long. You and your friend Christopher—”

“He’s not my friend!”

Aamir’s vehemence interested Strike.

“D’you own this house, Aamir?”

“What?”

“Just seems a big place for a twenty-four-year-old on what can’t be a big salary—”

“It’s none of your business who owns this—”

“I don’t care, personally,” said Strike, leaning forwards, “but the papers will. You’ll look beholden to the owners if you aren’t paying a fair rent. It could seem like you owed them something, like you’re in their pocket. The tax office will also consider it a benefit in kind if it’s owned by your employers, which could cause problems for both—”

“How did you know where to find me?” Aamir demanded.

“Well, it wasn’t easy,” Strike admitted. “You don’t have much of an online life, do you? But in the end,” he said, reaching for a sheaf of folded paper in the inside pocket of his jacket, and unfolding them, “I found your sister’s Facebook page. That is your sister, right?”

He laid the piece of paper, on which he had printed the Facebook post, on the coffee table. A plumply pretty woman in a hijab beamed up out of the poor reproduction of her photograph, surrounded by four young children. Taking Aamir’s silence for assent, Strike said:

“I went back through a few years’ worth of posts. That’s you,” he said, laying a second printed page on top of the first. A younger Aamir stood smiling in academic robes, flanked by his parents. “You took a first in politics and economics at LSE. Very impressive…

“And you got onto a graduate training program at the Foreign Office,” Strike continued, placing a third sheet down on top of the first two. This showed an official, posed photograph of a small group of smartly dressed young men and women, all black or from other ethnic minorities, standing around a balding, florid-faced man. “There you are,” said Strike, “with senior civil servant Sir Christopher Barrowclough-Burns, who at that time was running a diversity recruitment drive.”

Aamir’s eye twitched.

“And here you are again,” said Strike, laying down the last of his four printed Facebook pages, “just a month ago, with your sister in that pizza place right opposite Della’s house. Once I identified where it was and realized how close it was to the Winns’ place, I thought it might be worth coming to Bermondsey to see whether I could spot you in the vicinity.”

Aamir stared down at the picture of himself and his sister. She had taken the selfie. Southwark Park Road was clearly visible behind them, through the window.

“Where were you at 6 a.m. on the thirteenth of July?” Strike asked Aamir.

“Here.”

“Could anyone corroborate that?”

“Yes. Geraint Winn.”

“Had he stayed the night?”

Aamir advanced a few steps, fists raised. It could not have been plainer that he had never boxed, but nevertheless, Strike tensed. Aamir looked close to breaking point.

“All I’m saying,” said Strike, holding up his hands pacifically, “is that 6 a.m. is an odd time for Geraint Winn to be at your house.”

Aamir slowly lowered his fists, then, as though he did not know what else to do with himself, he backed away to sit down on the edge of the seat of the nearest armchair.

“Geraint came round to tell me Della had had a fall.”

“Couldn’t he have phoned?”

“I suppose so, but he didn’t,” said Aamir. “He wanted me to help him persuade Della to go to casualty. She’d slipped down the last few stairs and her wrist was swelling up. I went round there—they only live round the corner—but I couldn’t persuade her. She’s stubborn. Anyway, it turned out to be only a sprain, not a break. She was fine.”