“I’m in the main corridor,” Koko whispered. “The security guard, Marcus, is at the end of the hall. He’s looking at his phone.”

“Wait until he turns the corner toward the lobby,” I said.

My heart hammered against my ribs as I waited in the damp air of the station.

The smell of wet asphalt and train brakes filled my lungs.

“He’s moving,” Koko whispered. “Okay. I’m running to the service stairs.”

I heard the rapid patter of her rubber-soled shoes against the linoleum.

Then, the heavy thud of a fire door closing.

“I’m in the stairwell,” she said, her breathing heavy. “Going down to B1.”

“The air is colder down there,” I warned her. “And the lights are on a motion sensor. Give them a second to kick in.”

“It’s pitch black,” Koko murmured.

A moment of silence passed, filled only by the static of our connection.

“Okay, they’re on,” she said. “I see the chemical storage door. I’m at the keypad.”

“Zero, four, nine, two,” I repeated.

I heard the soft, rubbery clicks of the buttons being pressed.

A heavy metal click echoed through the phone.