Suddenly, the main computer screen on the center console blinked bright red.

A warning chime began to ring through the cockpit.

The satellite phone on the side panel lit up with an incoming call from our airline’s emergency dispatch.

I picked up the receiver and pressed it to my ear.

“Grace,” the voice on the other end said, urgent and breathless. “Do not touch the ventilation controls.”

“Why?” I asked, my grip tightening on the hard plastic receiver.

“We just pulled the security feed from the gate in Boston,” the dispatcher said, his voice cracking with static.

“Who is this?” I asked, pressing my free hand over my left ear to block out the steady hum of the flight deck.

“It’s Miller, from Flight Ops,” he said. “Listen to me carefully, Grace.”

I looked down at Captain Pierce, whose head was slumped against the cold glass of the side window.

His skin had turned a dull, waxy grey in the light of the instrument panel.

“A ramp agent was flagged on the tarmac twenty minutes before your pushback,” Miller said.

“He wasn’t on the ground roster for your flight.”