A fabulous jewel known as the 'Dark Star' is stolen; a pastor's daughter gets involved, falling into the depths of a spy plot concerning war plans and fortifications...

On an ocean liner returning to America, Alison Landis, an actress, avoids paying duty on a valuable pearl necklace by hiding it in the lining of a hat which she sends to Benjamin Staff, a playwright. The necklace is being trailed by a crook who is related to another passenger, Eleanor Searle, who also has a striped hatbox similar to the one recovered by the unsuspecting playwright. The crook bears an uncanny resemblance to Eleanor's father. The two bandboxes are inadvertently switched at the dock.