Mousy Mr. Humble, on a vagabond cruise, finds that being known as a private detective is more glamorous than admitting he is an accountant, takes it hard when he is asked to take charge of a murder -- later another- aboard the coastwise freighter. Able assistance is rendered by a cocky, memory trained girl, a frustrated actress, and a long lasting haunting is cleared up when Mr. Humble latches onto the killer. Gay to giddy.