Highly fictionalized early history of Canada. Trapper/explorer Radisson imagines an empire around Hudson's Bay. He befriends the Indians, fights the French, and convinces King Charles II to sponsor an expedition of conquest.

In 1667, French-Canadian trapper Pierre Esprit Radisson and his friend, Médard Chouart Sieur des Groseilliers, who is called "Gooseberry," try to interest the English governor of Albany in investing in a fur-trapping company centered in Hudson's Bay. Suspecting that the pair are rogues, the governor has them tossed in jail, where they meet Lord Edward Crewe. Edward, an English nobleman, was banished from England by Charles II due to his drunken pranks and Charles' desire to use his lands to rebuild London after the great fire of 1666. Edward convinces Radisson and Gooseberry to help him escape, and after reaching Montreal, they in turn persuade him to put up the capital for their expedition. Led by Orimha, Radisson's Indian foster father, the trio journey to Hudson's Bay, where they spend the winter trading with the Indians. As the months pass, Radisson tells Edward of his dream of a united Canada, in which white men and Indians work together to enrich the land. Radisson also explains that the Indians should be given needed trade goods for their furs, rather than useless trinkets or brandy. Upon their arrival at a French settlement, Radisson and the others are angered when the French governor, D'Argenson, seizes their furs as "payment" for fines enacted that morning. Resolving to interest King Charles in their venture, Radisson and Gooseberry steal back their furs and travel to England. Edward, nervous about Charles' reaction to his unsanctioned return to England, first takes his friends to meet Prince Rupert, the king's cousin. Impressed with Edward's success, Rupert escorts the trio to see the king, who forgets his anger after hearing Radisson's tales of the riches of Hudson's Bay. Not wishing to give the company an official charter until they have brought him 400,000 pelts, Charles allows Radisson to return to Hudson's Bay with more men, including Gerald Hall, the spoiled brother of Edward's sweetheart Barbara. Back in Hudson's Bay, the men establish their first trading post, Fort Charles. Tired of the cold and hard work, Gerald complains about having to travel furthur, and so Radisson leaves him at Fort Charles while he pushes on. One night, a wounded Indian arrives at Radisson's camp and informs him that after Gerald paid a band of Indian trappers with brandy, they went crazy and stole from a peaceful group in order to get more alcohol. Radisson rushes back to the fort, where he finds a drunken Gerald and an infuriated Orimha, who tells him that there will be a great Indian war unless Gerald is made to pay for his crime of inciting violence. Despite Edward's warnings that he will be hanged for murder, Radisson allows Gerald to be shot by a firing squad. Radisson, Gooseberry and Edward then escort the pelts to England, where Charles arrests them after hearing the story of Gerald's demise. Charles is compelled to reconsider, however, when he learns that Radisson instructed Orimha not to trade with the English if he does not return to Hudson's Bay. The trio are freed after Barbara reveals that she has forgiven them for Gerald's death, and she is then reconciled with Edward, while Radisson and Gooseberry exit the room singing.