On the refrigerator, held up by a magnet shaped like a propeller, was a postcard from Boulder, Colorado.
Dad, finals are killing me. Love you. Call Sunday. Emily.
His marriage had ended 9 years ago, when his wife left for a bigger life somewhere else. Their daughter had been 10.
Caleb could not be both an 80-hour-a-week engineer and the father she needed. So he walked away from all of it, and took a job that had him home by 4.
Emily was 19 now, studying mechanical engineering. The apartment had been this quiet since August.
He left the box unpacked, sat at the drafting table, and opened the photos on his phone beside the spiral notebook.
He flipped the notebook open to a page from 4 months earlier, written in his small, precise handwriting. A part number, a serial number, a note underlined twice.
Non-standard air data module installed on test article 2. Not on approved parts list. Reported to engineering. Report number attached.
The part number in the notebook matched the module feeding the diagnostic cart in the photo.
Caleb sat back slowly. He understood what it meant.
The air data sensors told a plane how fast it was flying, and at what angle it met the air. If one failed, a warning was supposed to tell the pilots which instrument to stop trusting.
But someone had installed a module that shouldn't be there. And killed the light that would warn anyone it was failing.
In icing conditions at altitude, a bad sensor could feed the flight computer false numbers, and nobody would have any reason to doubt them.
His phone buzzed on the table. Unknown number. This time it was a call.
He answered without speaking.
For a moment, there was only breathing on the line. Then a man's voice, low and unhurried, with the flat patience of someone reading from a script.
"You should forget about today, Mr. Mercer. Whatever you think you saw. For your own sake."
"Who is this?"
The line went dead.
Caleb stared at the phone. Then he stood, walked to the window, and looked down at the street.
A few parked cars, dusted with snow. A man walking a dog. Nothing out of place.
That was when someone knocked on his door.
Through the peephole, he saw a woman in a plain gray sweater and jeans. No security, no driver. A hospital bracelet still on her wrist.
He opened the door.
They looked at each other for a long moment.
"You should be in a hospital," Caleb said.
"I checked myself out."
Her voice was steady.