Grey leaves on another business trip and has Captain Brad Turner retain command of the Enterprise. Brad takes the Enterprise down the Missouri to deliver four cannons to Ft. Wilson, located in Sioux territory. However, the ship is running four days behind schedule because of a broken paddle wheel. As they approach Ft. Wilson, Brad and Joshua hear shooting ahead and order the men to turn out. They discover that the Sioux are attacking the fort and Brad fires a round of grapeshot from one of the cannons. The shock drives the Indians off and Brad takes a party to the fort. Lt. Henshaw greets them and explains that they've been under attack for three days, and that the commanding officer, Major Daniels, wants to see Brad right away.
Brad has the crew unload the cannons and accompanies Henshaw to the major's office. The lieutenant explains that they've lost several men and taken numerous injuries, and insists that the attacks started when Wilson insisted on enforcing discipline between his men and the local Indians. Brad figures it would take more than that to provoke the normally peaceful Sioux, and Henshaw admit that there was an incident where two underage Indian girls snuck into the fort to see the enlisted men. Daniels caught them and shaved their heads, and then sent them back to the tribes. Shaving an Indian's head is a major act of dishonor and the Sioux retaliated.
Daniels greets Brad and complains that they're four days late. When Brad mentions how Daniels set off the attack, the major angrily dismisses Henshaw when he realizes that the lieutenant told Brad what happened. Once Henshaw is gone, Daniels complains that his underling is a former river man and a poor officer as a result. Brad ignores the barb and asks Daniels to sign the receipt. He offers to take the wounded soldiers back, but Daniels changes tacks and pours him a drink. The major confirms that Brad has twenty men and explains that he only has fifteen men still capable of fighting.
Daniels' wife Barbara passes through on her way to tend the wounded, and the major introduces her to Brad. Once she leaves, Daniels informs Brad that he's pressing him and his men under military law, until he can get replacements from Fort Keo. Brad offers to take the Enterprise there, transport the injured soldiers, and relay Daniels' request faster than if he sends men by land. Daniel refuses even though he now has the cannons to defend the fort, and calls in Sgt. Matthews to take charge of Brad and his crew.
The crew bring the cannons up and Brad tells Joshua and Chip what has happened. As Joshua goes to tell the crew, Daniels comes out and offers to make Chip his orderly. The young boy is excited at his new duties and runs off. The major then confirms that Brad has a cook and orders Henshaw to take Pickalong to the cook house. The lieutenant respectfully points out that he's the only remaining artillery officer and his time might be better served dealing with the cannons. Daniels overrides him and sends him off, and then tells Brad that he'll deal with the cannons once they bury his men.
Pickalong checks out the cook house and assures Henshaw it's adequate. When he tries to discuss Daniels' attitude toward the lieutenant, Henshaw refuses to discuss it. Barbara runs over and confirms that the Enterprise is staying, and warns Henshaw that the wounded men will die without medical treatment. Pickalong assures her that Brad can handle himself, but Barbara worries that her husband will get them all killed. She goes into Henshaw's arms and he holds her close. Pickalong is surprised at the unexpected intimacy but tells Henshaw that he'll stand watch until Barbara regains control of herself.
That night, the crew is on watch when they spot a fire on the Enterprise. When Brad has his men form a bucket chain, Daniels overrides him. The major explains that he had his soldiers burn the boat to prevent Brad and the crew from escaping. When Brad warns him that he's making a mistake, Daniels gives him a receipt for the cost of the riverboat. As they argue about the price, the fire goes out and Matthews, who set the fire, insists that it couldn't have gone out on its own. Two Indians ride up, dump the corpses of the two soldiers who set the fire, and ride off before the men can shoot at them. Brad figures that the Indians want them scared and unable to run, but Daniels refuses to surrender to his opposite number, Running Bear. He orders Brad to be quiet or face imprisonment, and Brad agrees. However, he points out that he's only cooperating because they have no choice but to work together.
Later, Joshua stands watch with an enlisted man, Corporal Sam Turner. Turner starts to doze off but refuses to listen to Joshua when the mate suggests he get some rest. The corporal finally tells Joshua that Daniels wants one of his men watching each Enterprise crewmen at all times. Joshua wonders about the incident that started the war and Turner finally admits that the two enlisted men were in love with the Indian girls. When Daniels caught them together, he ordered Matthews to execute them on the spot and then shave the women's heads. Turner calls the fort "Fort Epitaph" in passing, and explains that the soldiers have nicknamed it because they figure they'll all be writing their epitaphs there.
In the officer's quarters, Barbara prepares to go out to tend the wounded. Her husband complains about her inability to have children and Barbara points out that he's never let her forget it. She wonders why he hasn't divorced her and then realizes that he could never become an officer serving in Washington without a wife on his arms. Daniels insists that he'll defeat the Indians using the new cannons and use his triumph to get a promotion to a Washington desk. Barbara is furious that he started the war just to advance his career, and Daniels insists that because he has no parents, no siblings, and no children, the only thing he can do to create a legacy is rise in rank.
Brad checks on Carney and Pickalong, standing watch on the wall. Carney asks how long they'll put up with Daniels and Matthews, and Brad assures him that he'll give them a sign if they have to turn against the soldiers. As they stand watch, Pickalong tells Brad about the incident between Barbara and Henshaw earlier that day.
When Matthews goes up to the guard post, he discovers that Turner has dozed off. When he kicks the man, Joshua tries to stop him and Brad and Carney come running. As Henshaw runs up, Joshua disarms Matthews and tells the lieutenant that he told Turner to get some desperately needed sleep. Brad defends Joshua's actions, pointing out that one man was on watch, but Henshaw reluctantly agrees that Turner disobeyed orders. However, he then tells Matthews that they'll use Joshua's suggestion and says that they'll ignore Turner's misconduct as a misunderstanding. Matthews is furious but Henshaw dismissively tells him to take it up with Daniels if he has problems with the orders.
A young Indian brave vaults the fort wall and sneaks inside.
Brad approaches Henshaw and asks his opinion about the major, but Henshaw refuses to commit himself. The captain mentions what Pickalong said and Henshaw insists that he was just comforting Barbara. As he refuses to question Daniels, Barbara comes out and tells Brad that her husband knew what he was doing when he humiliated the Indian girls. She admits that she had to talk to Henshaw because Daniels wouldn't listen to her, and Henshaw finally admits that Daniels started the Indian war to promote his career. The major was expecting the cannons four days ago but when they didn't arrive in time, Daniels lost face with the Sioux. Daniels wants to make sure that he defeats the Indians before his superiors get word of his earlier defeat, and plans to use the Enterprise crew to succeed.
The Indian brave sneaks into Daniels' quarters as the major lies sleeping, and leaves a narrow cut on his cheek. The major wakes up and the brave runs out, but the soldiers easily capture him. When he sees the cut on Daniels' cheek, Brad explains that the brave was counting coup on him, avenging the girls' humiliation. The captain realizes that only the son of a chief would venture into the enemy camp to attack an opposing chief, and Daniels realizes that the brave is Kicking Bear, Chief Running Bear's son. He has the soldiers tie the brave and Matthews tells Daniels about Henshaw pardoning Turner. Furious, Daniels relieves Henshaw of command and promotes Matthews to lieutenant.
Daniels tells Matthews that they're going to use Kicking Bear as bait to lure Running Bear into rescuing his son. The major scratches the brave's chest, counting coup on him, and promises Brad that he'll be avenged when he lures Running Bear into the front gate where the cannons are ready. Brad sarcastically admits that it's the greatest plan he's ever heard, and Daniels doesn't pick up on the taunt. The captain tells the major that he's going to bring him up before a board of an inquiry.
Men on both sides come running but Brad orders the Enterprise crew to drop their weapons. He then tells Daniels that they'll settle the matter per Army regulations. He tells the assembled soldiers that he can get them all to the Enterprise without anyone dying, and warns Matthews that if he follows Daniels orders to disaster then he'll lose his commission. Brad tells the soldiers to vote per Army regulations to declare Daniels unfit for command, and reminds Matthews that he'll take command. Matthews wonders what his plan is and Brad says that they'll return Kicking bear to his people. Daniels objects, refusing to turn over their hostage, but Matthews ignores his order to put Brad in irons.
Daniels threatens to shoot Brad for mutiny, but Brad points out that all of his men are now unarmed. All he's doing is calling for a vote per Army regulations, and suggests that Daniels won't get much support from his men at the board of inquiry. One by one, the soldiers put their guns down and cast their votes against Daniels. Matthews informs Daniels that he's no longer in command, and a furious Daniel throws his gun at the sergeant and walks off.
The next morning, Brad, Carney, and Pickalong take Kicking Bear and Daniels outside. Running Bear meets with them and smiles in satisfaction when he sees that his son scored coup on the Great White Major. The chief agrees that the girls' humiliation has been avenged and asks about Daniels. Brad assures him that the major will face justice from his superiors and turns Kicking Bear over. Running Bear agrees to let Brad and the others depart in peace, and watches as they depart.
As the Enterprise departs, Barbara tells Brad that she blames herself for what happened to Daniels. She asks Brad to let her husband lead his men into Fort Keo, keeping his dignity, and Brad says that he'll think about it. Later, he goes to Daniels and tells him that all of the enlisted men but one have agreed to let the major lead them to Fort Keo. Brad admits that Matthews was the lone dissenter, and Henshaw dissented because he's leaving the Army and returning to the river. Daniels agrees to give Henshaw his release and says that he'll deal with Matthews in his own time. When the major wonders why Brad is giving him the opportunity, Brad figures that Daniels has the potential to be a great officer. Daniels asks what Barbara has planned and Brad says that he has no idea, and tells Daniels that he has the run of the ship.
Later, the crew is drinking in the grand salon when a drunken Matthews staggers in and orders them to hand over the liquor. Carney refuses and they prepare to fight, but Daniels comes in and orders Matthews to stand down. He informs the lieutenant that he's demoting him to private, and Matthews swings at him. Daniels easily dodges the swing and draws his gun. When Matthews goes for his revolver, the major fires a warning shot and tells him to surrender. As Brad and Barbara run in to investigate the gunshot, Matthews says that he orders death by firing squad for Daniels. He goes for his shot and Daniels hesitates. The shot take him in the chest but he kills Matthews with his return shot. As the two men pass away, Barbara realizes that her husband deliberately let Matthews shoot him first so that he could take the honorable way out without dying at his own hand.
Later, Brad and Joshua are on the bridge when Henshaw comes up. The former lieutenant says that he plans to return to the river, and Joshua offers him the wheel and says that he'll put in a good word with Grey when the captain returns.