It seemed innocent enough: a paperback book propped in a doorway, allowing a sliver of light to escape from the staircase inside.
But at the bottom of that staircase, in the same basement lab room at the University of California -- Irvine, where it's been for the past 36 years sat the school's nuclear research reactor.
It was 1:15 a.m., and we'd come to UCI to see what security was like after hours.
Circling the building, we pulled the handle of every door. Every one was locked, save this one. Someone, perhaps a student or a researcher, had placed this paperback, "The Dancing Bees" (an out-of-print entomology text) in the doorframe just above the loading dock that borders the reactor room.
Instinctively, we looked around to see if anyone was watching us. No one was there.
Days earlier, we had already been inside the building. Five minutes after walking in the front door, we'd found ourselves standing outside an unlabeled basement lab, peering through a viewing window at a pool-type nuclear reactor.
There was no activity in the room -- just some computers and some large, silver, chemical canisters. Two security cameras clung to the ceiling in the hallway outside the reactor room, and the doors were locked.
While UCI is renowned for its physics and chemistry departments, which have produced three Nobel laureates in the past decade, its nuclear radiochemistry department keeps a much lower profile. In recent years, there has been declining support for the university's nuclear research and training reactor. According to reports in The Los Angeles Times and Orange County Register, campus officials have even considered shutting it down.
The reactor itself, however, remains operational. The professor in charge of the reactor was not available for a tour when we visited, but later informed us they only turn on the reactor a few hours a week for research and training.
Standing outside the propped door, we decided against removing the book and going in.
So we flipped our camera on "nightvision" and captured the scene. Who had left the book here? And would they come back? During our 15 minutes of filming, no one returned.
Karson Yiu is a Carnegie Fellow at Northwestern University. Steve Grove is a Carnegie Fellow at Harvard University.