In the warm months of 1849 twelve men leave Fort Leavenworth on a peace expedition to the far-flung Indian nations. Led by West Point-educated Captain Jedediah Owen, they take the American Fur Company steamboat up the Missouri River to Fort Union and then vanish into the wilderness. Months go by, and the army asks Jean Gallant, American Fur's finest scout, to search for the missing party. Gallant is more than happy to take on this assignment and visit his many Indian wives, but his inconclusive findings lead the army to believe the members of the peace party are dead. But Captain Owen's strong-minded fiancee, Susannah Saint George, refuses to believe that he is dead. She'll take a packet up the river come spring and find the Captain. She'll hire Gallant to lead her across the thawing plains to find the man who left her with the words, "Where the river runs, there will I be."