Milford Mouse is a detective who lives in the tallest building in the city. One day, a mouse from the countryside arrives at his office with a problem. The cheese in the countryside has disappeared, and the mice there are growing thin. They suspect a cat is behind it.

Milford agrees to help and travels to the countryside. He searches everywhere but finds no clues. After thinking carefully, he comes up with a plan. He places a piece of limburger cheese as bait and waits to see who takes it. By following the scent, he discovers the thief. This story follows Milford as he works through the case using observation and reasoning.