In London in 1763, Abby Hale Paulette Goddard is tried for the death of a Royal Navy officer that occurred when she tried to save her sick brother from the press gang. The judge condemns her to be hanged, then offers her the king's mercy: transportation to the British colonies in North America and a term of “not less than 14 years as an indentured servant, to be sold at auction.” She chooses the latter.
Aboard ship as it nears Norfolk, Abby incurs the anger of trader Martin Garth Howard Da Silva, who insists that the auction be held there and then. A bitter bidding war erupts between Garth and Captain Christopher Holden Gary Cooper, which Holden wins with an exorbitant bid. A friend reminds Holden he is engaged; he frees Abby, but afterward, his fiancée Diana Virginia Grey informs him that she has married his brother.
Meanwhile, Garth bribes the slave dealer into saying that Holden was only jesting and never bought her, destroying the bill of freedom. Garth takes Abby to the western frontier, where he is selling guns to the Indians toward the end of the French and Indian War. Holden’s friend John Fraser Ward Bond shows him something he got from an Indian who tried to kill him. Holden and Abby’s paths cross, but Garth convinces Holden that Abby came to him of her own accord.
Later, Garth makes it clear he is attracted to Abby. However, his Indian wife Hannah Katherine DeMille shows up with an important message. Garth hastily departs for a meeting. At the meeting are George Washington Richard Gaines, Colonel of the Virginia Regiment, his subordinate Holden, colonial governor Sir William Johnson Alan Napier, and others. They are deeply concerned about a possible native uprising. Holden fears that Pontiac will unite the tribes to wage war. Holden suggests sending someone to take “peace belts” to the Indians; Garth recommends Holden, and Holden accepts.
However, when Holden and his two companions are ambushed, he realizes that he needs to deal with Garth. When he comes for Garth, he is reunited with Abby, and their mutual misunderstanding is cleared up before they flee together to Fort Pitt.
When Garth comes for his alleged bond slave Abby, Holden provokes him into a duel. However, Garth has a bill of sale for Abby, so the governor awards her to him. Before Garth can do anything, he is summoned by Guyasuta, Chief of the Senecas Boris Karloff. He takes Abby along.
When a nearby settlement is wiped out, the governor prepares Fort Pitt for a siege. Holden walks unarmed into Guyasuta’s camp and, by trickery, manages to save Abby from being tortured to death. They escape and, seeing the aftermath of the massacre of settlers, head off to warn Fort Pitt against Indian treachery. However, Garth convinces the authorities that Holden is an untrustworthy deserter; Holden is sentenced to death and Abby is returned to Garth. She makes a bargain with Garth: she will willingly go with him in return for him arranging Holden’s escape. He agrees, but plots Holden’s death in the escape attempt. Hannah, having been told by Garth that he is abandoning her for Abby, warns Holden, takes his place, and is fatally shot.
With no more food left, the acting British commander decides to accept Guyasuta’s false promise to let them go unharmed. Fortunately, reinforcements arrive just in time, and the Indians flee. When the relief force enters Fort Pitt, the besieged see that the soldiers in the wagons are dead. Holden could not obtain reinforcements from the nearest British unit, which had suffered grievous casualties, but he is able to secure a token force of drummers and bagpipers from the Black Watch... and corpses. In the end, Holden kills Garth in a final shootout, freeing Abby to marry him.
