When the enigmatic Jedediah Smith, greatest of the mountain men, puts together a brigade of trappers for an expedition into the unknown territory of Mexican California , Sam Morgan joyfully joins up. With his Crow Indian wife Meadowlark and his coyote pup at his side, Sam sees the expedition as a chance for adventure -- and wealth.

Captain Smith leads the group south in search of the the Buenaventura, a great river believed to connect the Great Salt Lake to California, but when the river proves to be a myth, the trek toward the Pacific becomes a nightmare.

Like ghosts they struggle into the San Gabriel Mission in southern California and there recuperate, but the Mexican government eyes them with suspicion and Sam and his companions are forced to flee back into the Mojave.

When Meadowlark falls ill, Sam learns the poignant meaning of the words of his mentor, Hannibal McKye:

"Life is like a golden bear. It's magnificent, it's beautiful, and it bites."