Anthony Lorrimer charters the Enterprise to deliver a cargo of farm machinery to his thriving community of Lorrimer City. Captain Grey Holden is unaware that the cargo is actually arms and ammunition.

The Enterprise steams upriver with a cargo of arms and recruits for the Fort Union outpost. At Akins Landing, Grey Holden is told by Homer Atkins that the Sioux have been watching the boat and are planning an uprising.

The Enterprise, tied up overnight, is boarded and highjacked by a vicious crew, who kill the three men left to guard the boat. Captain Grey Holden and Ben Fraser return to the scene in time to see their craft heading down the river. They set out overland to head her off.

Bank robbers have a falling-out over some hidden loot. One of the men manages to give a map of the hiding place to his son, before he is killed. The boy heads up river on a raft to deliver it to his uncle.

Dan Duryea steps into the leading role for the first of two episodes.

The crew of the Enterprise planned a big night on the town. But when they dock, they find the place completely deserted, except for three new graves.

The Enterprise makes a wood stop at a small river town. But there is no wood for sale to strangers.

Gentleman Dan Muldoon is backing Dublin Boy against Gunner Stagle for the bare-knuckle championship of the river. Before the fight, Dublin Boy proves to have a glass jaw, when flattened by Grey, thus forcing the captain to take his place in the ring. Grey triumphs and becomes ""river champion.""