Ted Wilford and his friend, Nelson Morgan encounter mysterious goings-on at a greenhouse owned by the Bowens, a successful couple the Forestdale Town Crier has sent them to interview.

The principal target of the suspicious circumstances seems to be a lavender rose developed by Mrs. Bowen which she is getting ready to patent. Since the effort, skill, and facilities necessary to grow such a rose are considerable, it is important to find out who is trying to steal the records as well as the rose itself.

Beside learning a good deal about the operation of a moderately large commercial greenhouse, Ted and Nelson get mixed up in several midnight chases, including a dangerous one over a swamp to find someone who has been exposed to poisonous fumigants in the greenhouse. They also trace a forgery and search for a criminal with an apparent craving for salami.