Gambling-house proprietor Lionel Jamieson, whose brutality has caused his wife's paralysis, removes his stepdaughter Betty from a convent to use her as a lure for customers. Lionel's young employee Tommy is a good friend to Mrs. Jamieson and soon falls in love with Betty. With the assistance of stable hand Gunga Din, Tommy trains his horse, Thunderclap, for a racing event. At the gambling house, a customer is cheated out of $40,000 and threatens to kill Lionel unless he repays the money within 24 hours. Lionel's friend Foster agrees to help, provided that his horse wins against Thunderclap. Upon learning that Tommy will need to cross a bridge while transporting his horse to the racetrack, Lionel plots to blow it up, killing both Thunderclap and his owner. However, Gunga Din suspects foul play and ensures their safe arrival. Tommy then rescues Betty from kidnapper Wah Leong, returns to the track, and rides Thunderclap to victory. Lionel is killed by the man he cheated, and the shock restores Mrs. Jamieson's mobility.