In 1898 friends John Thomas and Lars Larson travel to the Yukon with their wives to make their fortunes. While in Alaska Thomas' wife gives birth to a boy, and Larson's wife has a girl, Julia. However, Larson spots a birthmark on his daughter's shoulder that resembles one on Thomas' shoulder, and he begins to suspect that he may not actually be the girl's father. Over the next 20 years the two become millionaires, but Larson's wife dies. Julia and Thomas fall in love and wish to marry, but Larson is determined to oppose it.

Irresponsible Billy Thorpe is sent to South America by his financée Claire's father, George Vincent, the rubber king, in order to reform.