The Slug Heist

A guard stretched at the security desk, eyeing the monitors scattered throughout the museum with disinterest. It was the overnight shift, so he wasn't watching crowds of guests bustle through; just a boringly still museum.

Meanwhile, in a glass display, a trio of tiny, trained slugs began a long, slow heist. They'd been deposited by their keeper earlier, but now, in low light, it was time to do their job.

The slugs slowly worked together to move a rare, highly-coveted gem the size of a quarter; their movements so slow, the guard never even noticed the gem was moving - even when it disappeared from the screen altogether.

Eventually, the guard stood to change places with a coworker, and he began his rounds around the museum. He'd walked the route three times and the sun was rising, but there was no familiar glint from the gem.

It was then he noted the absence.

The alarm was triggered; his coworkers on alert. They searched all over, but never found the gem.

It was only in the full illumination of daylight that they noticed the slimy trails on and in the case, but no one could fathom the slowest heist ever planned.