Sam Fisher- Thermal Vision Secrets

The first thing I do is circle the block and pop through the alley behind the store. There’s an expected employee exit but I also notice an unusual outline in the pavement on the ground next to the building. It’s almost as if someone had taken a stick and drawn a ten-foot-by-five-foot rectangle in the wet cement when it was first poured. Using my thermal vision, I notice there is heat beneath the outline—I can just make out thin slivers of light. Unlike most loading lifts that carry boxes to a shop basement, someone took great care to see that this one was hidden from view. Anyone without my training would never realize it’s there.
...

  I look inside the shop proper and find nothing out of the ordinary. The papers on the desk are invoices and such, neatly arranged and organized. I run my hand beneath the counter, searching for trick levers or buttons, but find none. Returning to the storeroom, I begin to examine the walls for telltale signs of secret doors. Again, my thermal vision comes in handy when I get to the bookshelf. Faint traces of light leak from the edges between two sets of cases. The access to the basement is behind them.

- Operation Barracuda, Chapter 20