At the door, he paused, listening to the soft bubbling of boiling water against a kettle lid, and the tinkle of teaspoons, and the opening of a cupboard. With one fingertip, he pushed open the kitchen door.

Janice spun round, eyes wide. On seeing him, she grabbed one of the china mugs on the tray and raised it hurriedly to her lips, but Strike had already taken a stride toward her. Gripping the thin wrist with his latex-gloved hand, forcing the mug away from her mouth, he felt bone beneath the soft flesh and the papery skin of the elderly. With his free hand, he pulled the mug out of hers, and examined it. A good inch of viscous white liquid was swimming in the bottom of it. Still holding Janice’s wrist, he looked into the teapot, which contained more of the same, then opened the cupboard over the kettle.

It was jammed with bottles of pills, weedkiller, bleach and jam jars full of what looked like home-dried plants, leaves and fungus: a poisoner’s storehouse, a testimony to a lifetime’s careful study of the means by which death could be delivered in the guise of healing.

“Think I’ll skip tea,” said Strike. “Let’s have a chat, shall we?”

She offered no resistance as he led her by the wrist back through to the sitting room and pushed her down onto the sofa.

“A murder-suicide would be a hell of a way to go out,” said Strike, standing over her, “but I don’t much fancy being victim number… how many is it?”

Janice said nothing. Her round blue eyes registered only shock.

Strike looked up at the wall of old photographs. One showed a toothy, beaming brunette bride, her hair worn in ringlets, in a high-necked lace dress, a pillbox hat on top of her veil, a large mole on her left cheekbone. Just above it was a picture of a young blonde with her hair worn in a frizzy eighties perm. She was wearing a red coat. He hadn’t noticed, hadn’t seen, because he’d walked into the room with certain expectations, making assumptions no less sweeping than Talbot had, with his conviction that Cancerians were intuitive, gentle and perceptive. Nurses were angels, ministering to the vulnerable: he’d been as guilty of bias as Vi Cooper, seeing Janice through the prism of his grateful memories of the nurses in Selly Oak who’d helped him manage pain and depression, and of Kerenza down in Cornwall, bringing comfort and kindness every single day. And on top of it all, he’d been fooled by a veritable genius for lies and misdirection.

“I thought,” said Strike, “I should come and tell the Athorns’ social worker in person that a body’s been found in their flat. You do a very good middle-class accent, Janice. I s’pose the phone Clare uses is round here somewhere?”

He looked around. Possibly she’d hidden it when she’d seen who was at the door. He suddenly spotted the hairdryer, tucked away behind the sofa, but with its lead protruding. He sidled past the coffee table, bent down and pulled it out, along with a roll of cellophane, a small phial with the label pulled off, a syringe and some chocolates.

“Leave them,” said Janice suddenly and angrily, but he laid the items on the coffee table instead.

“How ill would I have been if I’d eaten one of those dates you were doctoring when I arrived last time?” he asked. “You use the hairdryer to fix the cellophane back round them, right?” When she didn’t answer, he said, “I haven’t thanked you for those chocolates you sent Robin and me at Christmas. I had flu. Only managed to eat a couple before puking my guts up. Chucked the rest away, because they had bad associations. Lucky for me, eh?”

Strike now sat down in the armchair, beside his mobile, which was still recording.

“Did you kill all these people?” Strike asked, gesturing up at the wall of photographs, “Or do some of them just have recurrent bowel problems around you? No,” he said, scrutinizing the wall, “Irene’s not up there, is she?”

She blinked at him through the lenses of her round silver glasses, which were far cleaner than Dennis Creed’s.

A car came trundling up the road beyond the net curtains. Janice watched it pass, and Strike thought she was half expecting to see a police car. Perhaps she wasn’t going to talk at all. Sometimes, people didn’t. They preferred to leave it all up to the lawyers.

“I spoke to your son on the phone last night,” said Strike.

“You never!”

The words had burst out of her, in shock.

“I did,” said Strike. “Kevin was quite surprised to hear you’d been visiting him in Dubai, because he hasn’t seen you in nearly seven years. Why d’you pretend you’re visiting him? To get a break from Irene?”

She pressed her lips together. One hand was playing with the worn wedding ring on the other.

“Kevin told me he’s had barely any contact with you, since leaving home. You weren’t ever close, he said. But he paid for you to fly out there seven years ago, because he thought he should give you ‘another chance,’ as he put it… and his young daughter managed to ingest quite a lot of bleach while you were looking after her. She survived—just—and since then, he’s cut you off completely.

“We ended up talking for nearly two hours,” said Strike, watching Janice’s color fluctuate. “It was hard for Kevin to say out loud what he’s suspected all these years. Who wants to believe their own mum’s been poisoning people? He preferred to think he was paranoid about all those ‘special drinks’ you used to give him. And apparently your first husband—”

“He wasn’t my ’usband,” muttered Janice. “We were never married.”

“—left because he thought you were doing things to his meals, too. Kevin used to think his father was making it all up. But after our chat last night, I think he’s seeing things very differently. He’s ready to come over and testify against you.”

Janice gave a small convulsive jerk. For almost a minute there was silence.

“You’re recording this,” she whispered at last, looking at the mobile lying on the arm of Strike’s chair.

“I am, yeah,” said Strike.

“If you turn that off, I’ll talk to you.”

“I’ll still be able to testify to whatever you tell me.”

“I’m sure a lawyer would tell me not to let meself be recorded, though.”

“Yeah,” Strike acknowledged, “you’re probably right.”

He picked up the mobile, turned it to face her so she could watch, switched off the recording, then laid it down on the small coffee table beside the chocolates, the empty phial, the syringe, the cellophane and the hairdryer.

“Why d’you do it, Janice?”

She was still stroking the underside of her wedding ring.

“I don’t know why,” she said. “I just… like it.”

Her eyes wandered over the wall of photographs.

“I like seeing what ’appens to them, if they take poison or too many drugs. Sometimes I like ’elping ’em and ’aving them be grateful, and sometimes I like watching ’em suffer, and sometimes I like watching ’em go…” A prickle ran up the back of Strike’s neck. “I don’t know why,” she said again. “I sometimes fink it’s because I ’ad a bang on the ’ead, when I was ten. My dad knocked me downstairs. I was out for fifteen minutes. Ever since then, I’ve ’ad ’eadaches…’Ead trauma can do fings to you, you know. So maybe it’s not my fault, but… I dunno…

“Wiv me granddaughter,” said Janice, frowning slightly, “I just wanted ’er gone, honestly… spoiled and whiny… I don’t like kids,” she said, looking directly back at Strike. “I’ve never liked kids. I never wanted ’em, never wanted Kev, but I fort if I ’ad it, ’is dad might marry me… but ’e never, ’e wouldn’t…

“It was ’aving a baby what killed my mum,” said Janice. “I was eight. She ’ad it at ’ome. Placenta previa, it was. Blood everywhere, me trying to ’elp, no doctor, my father drunk, screaming at everyone…

“I took this,” said Janice quietly, showing Strike the wedding ring on her finger, “off Mum’s dead ’and. I knew my father would sell it for drink. I took it and ’id it so ’e couldn’t get it. It’s all I got of ’er. I loved my mum,” said Janice Beattie, stroking the wedding ring, and Strike wondered whether it was true, whether head trauma and early abuse had made Janice what she was, and whether Janice had the capacity to love at all.

“Is that really your little sister, Clare?” Strike asked, pointing at the double frame beside Janice, where the sleepy-eyed, overweight man with smoker’s teeth faced the heavy but pretty blonde.

“No,” said Janice, looking at the picture. After a short pause, she said, “She was Larry’s mistress. I killed both of ’em. I’m not sorry. They deserved it. ’E was wiv me, ’e wasn’t much of a catch, but ’e was wiv me, the pair of ’em carryin’ on be’ind my back. Bitch,” said Janice quietly, looking at the picture of the plump blonde.