Watch Thou Art the Man (1920) Official Trailer

Suspicious that his employers are diamond smugglers, soldier-of-fortune Myles Calthrope quits his job in the African mines and heads south, where he meets and falls in love with Joan Farrant. Joan, unaware that her brother Henry is in the diamond smuggling business, obtains Myles a position in the family firm. Myles is given an envelope of legal documents to deliver, but when he is searched aboard ship, diamonds are discovered in the pouch and Myles is imprisoned. After completing his sentence, Myles secures a job on the Prescott sugar plantation, where he once again meets Joan, who denounces him as a smuggler. Mr. Prescott, Myles's employer, determines to prove Myles's innocence.