A young man in the California gold rush, on a mission to deliver supplies by mule train to the new miners in the rugged Yuba River Valley, must go after ruthless bounty hunters who kidnapped the party's Chinese cook with the intention of returning him to the cruel whaleboat captain from whose ship the cook fled when it docked in San Francisco. After getting information in the new boom town of Nevada City, the young man realizes he must catch the kidnappers before they reach the port of Marysville and leave on a steamboat never to be seen again.