Every hour, my toddler would walk to the same corner of his room and press his face against the wall. At first, I convinced myself it was just a phase. Kids do odd things all the time. But the day my son finally said something about it, everything shifted.

Ray stepped back, wiping plaster dust off his forehead, staring at the exposed metal with open-mouthed astonishment. "What the hell... Mark, this house was built in 1928. That looks like an old wall safe or an in-wall intercom system."

I dropped to my knees in front of the opening. The air coming out of the hole smelled stale, damp, and metallic—like cold copper and old grease.

"Look at the speaker grill," I pointed out, my voice barely a whisper.

The mesh was torn in the center, and running from behind the brass casing were two modern, clear-insulated copper speaker wires. They weren't ninety years old. They were clean, shiny, and had been routed down into the floor cavity recently.

Someone had wired a modern audio feed directly into an antique wall safe hidden inside my son's bedroom.

"Ray," I said, my pulse racing. "Where do those wires go?"

Ray pulled out a heavy flashlight and shone the beam into the narrow gap between the metal safe and the wooden studs. The two copper threads disappeared down through a freshly drilled hole in the subfloor, dropping directly into the space between the second floor and the first-floor ceiling.

"They go down," Ray said, his tone turning cautious and dark. "Toward the kitchen or the basement."

"Watch Ethan," I told him, standing up so fast the room spun for a second. "Don't let him come up here."

I ran down the stairs, bounded through the kitchen, and opened the heavy wooden door leading to the basement.

The basement was a dark, unfinished space with exposed stone foundation walls, an old oil furnace, and rows of dusty wooden shelves packed with old paint cans and holiday decorations.

I grabbed a flashlight off the workbench and shone it up at the exposed floor joists overhead.

Tracing the path from directly beneath the nursery corner, I saw the two clear speaker wires snaking along the wooden beams. They didn't end at the electrical panel. They ran all the way across the basement ceiling, following the main support beam toward the far corner of the cellar—where an old disused Coal Chute door led out under the back porch.

Taped to the underside of one of the joists was a small, black plastic box no bigger than a deck of cards.

A wireless audio receiver.

Beside it was a small lithium-ion battery pack, its blue LED light blinking steadily in the dark.

My breath hitched in my chest.

This wasn't a ghost. It wasn't an environmental resonance or a child's imagination.

Someone was broadcasting audio directly into the wall of my son's bedroom from outside the house. Someone was speaking to Ethan while he lay in his crib.

I reached up, ripped the receiver off the joist, and examined it. It was a standard baby monitor relay—a high-frequency transmitter hacking into the exact frequency of the digital monitor I had bought four months ago.

My phone rang in my pocket, the loud vibration making me jump.

I pulled it out with trembling hands. It was Dr. Mitchell.

"Mark," she said urgently as soon as I answered. "I just got the background checks back on the temporary care agency you used three months ago. The second nanny—the one Ethan cried around?"

"What about her?" I demanded, holding the black receiver tight in my fist.

"Her name isn't Sarah Jenkins. She used a stolen social security number," Dr. Mitchell said, her voice heavy with alarm. "And Mark... two years ago, before your wife passed away, she worked briefly as an associate at a private medical research firm. Does the name Aegis Dynamics mean anything to you?"

I felt the room tilt around me.

Aegis Dynamics.

My late wife, Clara, had been a biostatistician. Three weeks before she went into sudden, fatal heart failure during labor, she had resigned from Aegis, claiming she had found critical irregularities in their clinical trials. I had been so overwhelmed by her sudden death and the shock of raising Ethan alone that I had never looked into her work files. I had buried her research notes in an old lockbox in the attic.