He took a deep breath and let it out. There was a flashlight in one of the drawers down in MRI. He knew exactly where it was; he’d put it there himself, more than a year ago.

He reached back and found the wall again. Inching to his left, his foot ventured toward where he knew the edge of the first step would be. It was there, as was the railing. Mike lowered himself down. With the railing in hand it became easier to move forward, and he fumbled down the next six steps without incident, finding himself on the landing. If he turned ninety degrees and reached out with his right hand, he could follow the next dozen or so steps to the ground floor. From there he could feel his way down the hall to the MRI control room, to the drawer beneath the microwave, and when he got the flashlight he would reevaluate his options. He would—

Below him, in the darkness, something shifted.

Mike froze, clutching the railing, his eyes helplessly held wide against the blackness. His heart was booming in his ears like far-off artillery. The big ventilation fans had all stopped when the power went out, and the stairwell was quieter than he’d ever heard it.

Something moved down there. I know it.

He tried to think of what kind of noise it had been. A shuffling sound, like a shoe scraping? Or was it the rustle of fabric? Or a cough? Sarah would’ve known.

Now there was nothing.

Mike held his breath. He could almost feel his auditory canals reaching out to search the darkness like long antennae and coming back empty.

But he would have to walk through that nothing to get to where he was going.

Ask yourself this: How certain are you that you even heard something in the first place?

In the end it didn’t matter. He could stand here forever. There was only one light source in this entire hospital whose location he was absolutely sure of, and to get it, he’d have to go straight down those stairs.

Count to sixty. If you haven’t heard anything by then, go ahead.

He started to count. It didn’t take as long as he’d thought, so he kept counting until he reached a hundred. And then two hundred. Still no sound.

For the first time his mind opened itself to the possibility that he really could have imagined the noise, or if not, it might have had a perfectly normal explanation, a creaky pipe, an old foundation, some mundane sound he would never have noticed under normal circumstances. He found he’d begun to visualize the bottom of the stairs with no one there—no one had been there to begin with.

He started moving again, easing down the steps like a man wading into very cold water, one shuffling step, and then the next. Every few seconds his chest would start aching and he realized he was forgetting to breathe.

Here’s where I feel the hand grab me. Or the knife slides into my spine. Right now. Here’s where the fingers take hold of my throat—