|Harold Lloyd||Harold Bledsoe|
|Barbara Kent||Billie Lee|
|Douglas Haig||Buddy Lee (uncredited)|
|Noah Young||Patrick Clancy|
|Charles Middleton||John Thorne|
|William Walling||Capt. Walton|
|Edgar Kennedy||SFPD Desk Sergeant (uncredited)|
Milquetoast botanist Harold Bledsoe reluctantly travels to San Francisco to take over his late father's position as a high-ranking police detective. Despite the meddling of a crotchety sergeant and the bluster of an outraged community leader, Harold begins an investigation of a Chinatown opium smuggling ring led by a mysterious figure known as the Dragon, while also wooing the tomboyish pixie Billie Lee .