The Galloping Jinx (1925)

Madge Walling's uncle dies and leaves her his ranch, but with the proviso that she be married by noon on the day she turns 18 years of age. Harold Rice, the man she is to marry, is held up by bandit Pete Black and doesn't arrive at the ranch on time. Secret Service agent Rankin manages to recover Harold's money from Black, but is injured in the process and suffers amnesia. He wanders onto the Walling ranch, where he is mistakenly assumed to be Rice. Complications ensue.