I hastily pressed cancel, and clicked through to the camera icon. The screen showed me a view of the front door, but the outside light was not on, and inside the shelter of the porch I could see nothing but grainy pixelated darkness. Had Jack come back? Had he forgotten his keys? Either way, as the doorbell sounded for the third time, I could hear the chimes filtering up the stairwell as well as coming out of my phone, and I knew I had to answer it before the noise woke the girls.

The room was unnaturally cold, and I pulled on my dressing gown before padding quietly downstairs, my feet soft on the thick carpet runner, picking my way in the semi darkness but not wanting to turn on the lights and risk waking the children. In the hallway I had a moment’s struggle with the thumb panel, and then the door swung silently open to reveal . . . nothing.

It was quite dark. The Land Rover’s parking space was still empty, and none of the motion-sensitive security lights around the yard were on, though the porch light flicked on as soon as I stepped over the threshold, detecting my presence. I shaded my eyes against its harsh glare and peered across the yard and down the drive, shivering slightly in the cool night air. Nothing. There were no lights on in Jack’s flat either. Had something triggered it by mistake?

Closing the door, I made my way slowly back up towards my bedroom, but I was barely halfway up the second flight when the bell sounded again.

Damn it.

With a sigh, I belted my dressing gown tighter and made my way back downstairs, hurrying this time.

But when I wrenched open the door, again, there was no one there.

I slammed the door harder than I meant to this time, the tiredness making my frustration boil over for a second, and I stood in the dark of the hallway, holding my breath and listening for a sound from upstairs, the rising siren of Petra’s wail perhaps. But none came.

Nevertheless, this time, instead of setting back upstairs to my own room, I stopped and peered in at Petra, sleeping peacefully, and then into Maddie and Ellie’s room. In the soft glow of their night-light I could see both of them lying fast asleep, sweaty hair strewn across the pillows, their cherubic little mouths open, their soft snores barely disturbing the quiet. They looked so small and vulnerable in sleep, both of them, and my heart clenched at my anger towards Maddie that morning. I told myself that tomorrow I would do better—that I would remember how young she was, how disorienting it must be to be left with a woman she barely knew. Either way, it was clearly not one of them playing with the doorbell, and I shut the door softly and made my way back upstairs to my room.

It was still very cold, and as I closed the door behind me, the curtains billowed out, and I realized why. The window was open.

I frowned as I walked across to it.

It was open, and not just slightly, as if someone had wanted to air the room, but completely open, the bottom sash pushed up as high as it would go. Almost—the thought came unbidden—as if someone had been leaning out to smoke a cigarette, though that was absurd.

No wonder the room was cold. Well, it was easily solvable at least—easier than battling with the control panel at any rate. The curtains, doors, lights, gates, and even the coffee machine in this place might be automated, but the windows at least were still Victorian originals, blessedly operated by hand. Thank God.

I yanked the sash down, drew the brass catch across, and then scampered back into the still-warm sanctuary of the feather duvet, shivering pleasurably as I snuggled into its folds.

I was drifting back off to sleep when I heard it . . . not the doorbell this time, but a single, solitary creeeeak.

I sat up in bed, my phone clutched to my breast. Shit. Shit shit shit.

But the next sound did not come. Had I misheard? Was it not the footsteps that had woken me the night before, but something else . . . ? Just a branch in the wind, perhaps, or an expanding floorboard?

I could hear nothing apart from the whoosh of my own blood in my own ears, and at last I lay slowly back down, still clutching my phone in my hand, and shut my eyes against the darkness.

But my senses were on high alert, and sleep seemed impossible. For more than forty minutes I lay there, feeling my pulse thumping, feeling my thoughts race with a mixture of paranoia and wild superstitions.

And then, half as I’d feared, half as I’d been waiting for, it came again.

Creeeeak . . .

And then, after the smallest of pauses, creak . . . creak . . . creak . . .

This time there was no doubt—it was pacing.

My heart leapt into my throat with a kind of nauseating lurch, and my pulse sped up so fast that for a moment I thought I would faint, but then anger took over. I jumped out of bed and ran to the locked door in the corner of the room, where I knelt, peering through the keyhole, my heart like a drum in my chest.

I felt absurdly vulnerable, kneeling there in my nightclothes with one eye wide open and pressed to a dark hole, and for a moment I had a sick, jolting fantasy of someone shoving something through the hole, a toothpick perhaps, or a sharpened pencil, roughly piercing my cornea, and I fell back, blinking, my eye watering with the dusty draft.

But there was nothing there. No toothpick maliciously blinding me. Nothing to see either. Just the unending blackness, and the cool, dust-laden breeze of stale attic air. Even if there was a turn in the stair, or a closed door at the top, with a light on in the attic itself, some light would have escaped to pollute the inky dark of the stairs. But there was nothing. Not even the smallest glimmer. If there was someone up there, whatever they were doing, they were doing it in the dark.