I scan the room, assessing my options. Stacey is blocking the only doorway. No windows or skylights. There’s a large cage of machinery in the far corner next to the chest freezer: a mechanical pump of some kind. At a guess I’d say it’s for the swimming pool. The small external access hatch above it is probably the source of the fresh air I can feel. Even if I could get free and reach it, it’s far too small for me to climb through.

My only hope is to talk my way free.

‘Felix has been down here all along,’ I say. ‘You’ve kept him locked in here for five weeks.’

‘Literally right under everybody’s feet,’ Stacey says. ‘All those people looking for him, DCI Hollander and DS Mehdi telling me they’d leave no stone unturned to find him, and he’s been right here all along. You’ve got to admit it’s funny.’

‘No one even knew the cellar was here?’

‘Exactly. Not even Felix, until I showed it to him. It’s not on any architectural plans. I only found it by accident a couple of years ago, when I was considering putting in an outdoor shower and discovered the internal dimensions of the corridor upstairs didn’t match the external measurements. I located the stairs to the cellar by a process of elimination. Felix said it’s like one of those secret dungeons in a medieval castle – what’s the name for them?’

‘An oubliette,’ I say.

She comes a little closer to me, but she’s still out of my reach. I deliberately let the bottle of water slip from my hand so it rolls towards her, and she takes another step in my direction to catch it. She’s not foolish enough to hand it to me, though: instead she simply tightens the lid and rolls it back.

‘Why keep him alive?’ I ask conversationally. ‘Why not save yourself the trouble of looking after him?’

‘I didn’t want to kill him,’ she says, sounding almost indignant. ‘That was never the plan.’

‘Then why is he here?’

‘It was his idea,’ Stacey says.

I’m stunned. ‘Felix wanted you to chain him in the cellar?’

‘Not exactly,’ Stacey says. She perches on the chest freezer, gently swinging her legs. ‘It’s a long story.’

‘I’m not going anywhere.’

She laughs. ‘Fair enough. Would you be surprised if I told you it was all about money?’