In 1804, Captain Meriwether Lewis and Second Lieutenant William Clark set out on an expedition to explore the uncharted American frontier. They have been tasked by President Jefferson with clearing the way for America's western expansion.

Believed to be inhabited by monsters, Lewis begins to question the motives of their trip in his journal, proclaiming "birds, small game and Indians" are the only thing to be found. Just before reaching Charrette, the most western American settlement, the Corps come upon a large structure along the Missouri River.

They land near the object and being to study and sample the surrounding area. Suddenly, the party is attacked by an unknown beast. Lewis, caught completely off-guard, stumbles to the ground as the monster charges towards him. Clark fires his pistols and pierces the beast's chest, which drops to the ground. Standing over the corpse of this strange creature, The Corps of Discovery soon realize the reality of the task at hand.