Miss Simpson, the daughter of a wealthy London banker, goes on a visit to Paris. A gang of jewel thieves learn that she is carrying her valuable jewelry with her. Immediately on the arrival of the steamer on which she crosses the Channel, they follow her into the train. A female accomplice makes friendly advances in a railway carriage, and at luncheon contrives to place a drug in her wine. The scheme is successful up to that moment, but the thieves are not aware that Gerald, a smart young detective, has kept a watchful eye upon them. The detective skillfully turns their plots so that they turn against the plotters, and when the train arrives in Paris, he has the birds nicely trapped. They are handed over to the police, whilst Miss Simpson proceeds to her hotel to rest after her eventful journey.