A clerk at a nuclear power plant steals some plutonium and hides it in a large hotel. When he’s dying as the result of an accident, he manages to give a one-word clue as to the plutonium’s location before passing on, and a clever agent is able to understand the meaning of the clue.
This is an extraordinarily weak story. It resembles nothing so much as one of the Griswold stories from The Union Club Mysteries—"Dollars and Cents,” to be precise, which shares with it the idea of searching for something dangerous hidden in a hotel.
So weak and forgettable is the story, in fact, that when I originally reviewed Thirteen Horrors of Halloween (which includes it) I casually mentioned that the book contained no Asimov stories at all. That this tale was there managed to slip past me entirely.