Richie shook his head. “Why, but? They were big enough to come get their ma if they needed her. And it’s not like this is a massive huge mansion: if they hurt themselves, you’d hear them yelling.”

I said, “Would you know the other halves of those things if you saw them?”

“Probably.”

“Good. Then let’s go find them.”

On Emma’s pink chest of drawers was a round white thing like a clock radio, which according to Richie was an audio monitor: “She’s a little old for it, but the parents could’ve been heavy sleepers, wanted to be sure they’d hear her if she called …” The other audio monitor was on Jack’s chest of drawers. No sign of the video cameras; not until we got back out onto the landing again. I said, “We’ll want the Bureau to check the attic, in case whoever was looking for—” and then I swung the torch beam up to the ceiling and stopped talking.

The hatch for the attic was there, all right. It was open onto blackness—the light caught the cover, propped up against something, and a flash of exposed roof beam high above. Someone had nailed wire mesh over the opening, from below, without worrying too much about aesthetics: ragged edges of wire, big nail heads sticking out at violent angles. In the opposite corner of the landing, high on the wall, was something silver and badly mounted that I didn’t need Richie to tell me was a video monitor. The camera was pointing straight at the hatch.

I said, “What the holy hell?”

“Rats? The holes—”

“You don’t set up bloody surveillance on rats. You keep the hatch down and call the exterminators.”

“Then what?”

“I don’t know. A trap, maybe, in case whoever bashed in the walls came back looking for Round Two. The Bureau are going to want to be careful up there.” I held the torch high and moved it around, trying to get a glimpse of what was in the attic. Cardboard boxes, a dusty black suitcase. “Let’s see if the rest of the cameras give us any hints.”

The second camera was in the sitting room, on a little chrome-and-glass table beside the sofa. It was aimed at the hole over the fireplace, and a little red light said it was switched on. The third one had rolled into a corner of the kitchen, where it was surrounded by beanbag pellets and pointing at the floor, but it was still plugged in: it had been up and running. There was a viewer half under the cooker—I had clocked it the first time round, taken it for a phone—and another under the kitchen table. No sign of the last one, or of the other two cameras.

I said, “We’ll give the Bureau a heads-up, have them keep an eye out. Anything you want another look at, before we bring them in?”

Richie looked unsure. I said, “It’s not a trick question, old son.”

“Oh. Right. Then no: I’m grand.”