Andrew Bullivant, a retired lawyer known as "Grumpy" for his irascibility, calls on all his experience and powers of deduction to expose Chamberlin Jarvis as the thief of a valuable diamond being transported by Ernest Heron. A gardenia is the clue; and Virginia Bullivant, Ernest's sweetheart, is Jarvis' unwitting dupe.

Donald Grant, after serving a prison term, obtains a job in a smalltown factory where he meets Helen Wilburton, who invites him to board with her and her father. He marries her, and on the first night of their honeymoon, a burglary is traced to one of Donald's former cohorts.