In St. Louis, the Enterprise is tied up at the dock when actress Lorna Langton and her manager, David Fields, arrive. Lorna asks to charter the ship for a trip to Red Bluff to arrive the next day. When Grey points out that there's nothing there but an abandoned trading post, Lorna simply says that she wants to leave immediately. Aware of her career as an actress, Grey tells her that half is crow are ashore on leave and the ship doesn't have a head of steam. However, she offers him $2,000 to make the trip immediately. Intrigued, Grey wants to know why she's making the trip. Lorna will only say that she'll tell him once they're en route, she'll explain and if Grey doesn't like it he can turn the ship around and keep the money. Grey accepts and goes to get the crew, while Lorna turns to Luke Cragg, a scruffy drifter who has been sitting nearby on the deck. She tells him that the rest is up to him and Luke says that will satisfy him just fine.
Grey goes to the pilothouse, calls down to Carney, and tells him to bring the boilers up to steam. When Ben comes up, Grey tells him what's going on and that they'll operate with a skeleton crew of six men. Happy to be transporting the famous actress, Lorna Langton, Ben goes to work.
Once Lorna goes to her cabin, she tells her manager that he doesn't have to come with her. David insists that he wouldn't stay behind and that her happiness means everything to him. As David leaves, Grey stops by to tell Lorna that they'll be leaving shortly and that they'll make the trip without a cook. She tells him not to worry about it and to get under way.
Once the boilers have a head of steam, the Enterprise heads into the river. Gray checks on Travis, who is serving as cook, only to find Linda preparing dinner. She explains that her husband was a ship's cabin and she knows how to handle a galley and a ship. Lorna then explains that they're going to Red Bluff because her son Bobby may be there. Six years ago she and her husband were traveling west and were attacked by Indians. They killed her husband and took the five-year-old boy prisoner.
David enters the grand salon and explains that Luke told them that his family took a white boy from the Sioux. They've heard from other men before, but they've all turned out to be wild goose chases. When Lorna shows Grey a watch fob that Luke claims came from the boy, David points out that it's just like hundreds of others. Grey admits that the whole thing is a long shot and David agrees with him, but Lorna insists on pursuing the matter. When Lorna goes back to the kitchen, David complains that Lorna should be focusing on her career. Luke comes in for food and Grey asks why they have to be there in 24 hours. The man doesn't give a straight answer but simply insists that he wants Lorna to cover his family's expenses on top of the $500 she has already paid. David tells him that he won't get any more money, and Luke responds by saying that David wants her money for himself as her manager. David takes offense and goes for a dinner knife, and Luke grabs another one, but Grey slams a coffeepot down between them. As Lorna comes out, Grey tells her that he doesn't like being part of a swindle and leaves.
When Gray goes up to the pilothouse, he tells Ben that he doesn't trust their passengers. When Ben goes down to get some food, Lorna comes up to see gray and asks if he's going to accept the charter. The captain admits that he's having second thoughts and Lorna shows him a cameo photo of her husband. She explains that he was the only man who ever made her happy and that she'd do anything to get her son Bobby back as a reminder of her husband. When Lorna says that she plans to retire to raise the child, Grey wonders if her manager will be happy with the decision, but the actress insists that David wants the best for her. Grey agrees to continue the trip and Lorna thanks him.
As Lorna goes below, Luke grabs her and demands to know what Grey said. Once Lorna tells him that they're continuing to Red Bluff, Luke grabs her and warns that unless she responds to his advances, she won't see Bobby again. Grey hears them struggle and comes down to slug Luke. Luke vows to get even later but the captain dismisses his threat.
The next day, the Enterprise arrives at Red Bluff and Grey waits while Luke goes to get his family. He enters the abandoned trading post and greets his father Josiah and his three brothers, Matthew, Mark, and John. Luke tells them that there are only six men aboard the Enterprise and Josiah tells him to bring everyone over. Luke brings Lorna, David, and Grey into the trading post and Josiah welcomes them, talking insincerely about how heartwarming it is to reunite mother and child. He then tells Lorna that he locked Bobby up in the next room because he's excitable. When Josiah explains that Bobby doesn't speak much English, Grey offers his services as a translator and goes in with Lorna.
Inside the room, the boy Josiah claims is Bobby hides in the corner. Lorna isn't sure if it's Bobby given the age and the clothing, and the boy refuses to respond. When Lorna offers him some peppermint candy, he bites her hand. The actress tries a second time and the boy spits it out because of the taste. However, Lorna offers him a second piece and the boy, used to the taste, eats it. He then picks up the first piece from the floor but Lorna gives him a clean piece instead. The boy then answers Grey's questions, explaining that his tribe was small and they never gave him a name.
Josiah comes in to see how they're doing and the boy cowers back. Once the father ushers them out, he insists that the boy is Lorna's son because the Sioux chief he bought him from said he obtained the boy in a raid. Josiah then orders his sons to capture the trio and demands all of the money Lorna has. He also wants the money that Lorna paid Grey, and plans to take the Enterprise to sell. The Craggs take Grey, Lorna, and David to the ship, using them as hostages. However, once the trio gets aboard the Enterprise, Grey yells to Ben, who is ready to cut one side of the gangplank loose. The Craggs drop into the water and the crew fishes them out and puts them to work in the boiler room.
The Enterprise leaves for St. Louis and Grey talks to Josiah. The old man admits that he has no idea if the boy is really Bobby Langton. Satisfied that the whole thing was a con, Grey checks on Lorna and hears her singing to the boy. She tries to kiss him good night, explaining that she did the same for her son, but the boy cowers away. Lorna asks him if he remembers his father and the boy mutters the word "father" but shakes his head. Upset, he takes Lorna's hand and she tells him that everything will be all right.
The next day, Lorna trims the boy's hair and shows him his reflection, which startles him. Grey comes in with borrowed clothing from the crew and explains that the Sioux consider long hair a symbol of a man's strength. When Lorna goes out to let Bobby change, he hesitantly asks her to stay, and she assures him that she'll be right outside the cabin. Grey gets the boy dressed and has him practice speaking English, and then brings Lorna and David in to see the boy. Lorna is clearly taken with the boy but David reminds her that she agreed to stop seeing him and risk an attachment since he's not her son. The manager wants to turn the boy in immediately so they can find his parents, but Grey suggests that they give him time to remember. David refuses, saying that Lorna has a booking in St. Louis and that she shouldn't postpone it because of another family's child. The boy hesitantly starts describing his father, matching the description of Lorna's husband. However, she realizes that the boy stole her cameo and is lying to her.
Grey takes the boy around the ship and tries to explain about why he should tell the truth. When they go to the boiler room, the boy recognizes the Craggs and backs away, but Grey assures him that they're under control. However, he realizes that Carney is dozing off on guard duty and kicks him awake. The boy doesn't remember anything about ships, despite the fact his father was a ship's captain, and Grey continues his tour. He takes the boy to the pilothouse but the boy doesn't remember a ship's wheel. Grey is ready to give up but the boy admits that he doesn't want to fail and make Lorna sad.
In the grand salon, David tries to discuss Lorna's career but she's still focused on the boy. Grey brings the boy in as Lorna reluctantly admits that she's done trying to find her son. She goes out and Grey leaves the boy with David while he goes after her. Out on deck, Grey admits that the boy doesn't remember anything about ships but he's a nice kid. Meanwhile, inside, the boy starts talking about a big sailing ship. He calls to Lorna, who runs back in, happy that the boy can remember something from Bobby's past. However, David claims that he told the boy about the ship, and Lorna assumes the boy is lying and walks away.
Later, the boy puts his Indian clothing back on and then goes outside to the rail. Grey spots him and grabs him just as he prepares to jump overboard. As Travis locks the boy in his cabin, Lorna wonders why the boy would have jumped and Grey angrily tells her that the boy needs love even if he isn't her son. The captain accuses Lorna of wanting a son just so she can play the role of a mother and tells her that the only real proof any mother needs about her son is that she loves him. As Grey walks away, David comes over and Lorna admits that the captain was right. She vows to raise the boy as her own even if he isn't Bobby, and figures that he lied because he needed her... and she admits that she needs him. When Lorna says that she's canceling her stage engagement, David grabs her arm and wonders if she'll cancel him as well after all of his hard work on her behalf. Lorna tells him to let her go and walks away, and David lashes out in fury.
Lorna goes into the boy's cabin and apologizes for rejecting him. The boy, crying, accuses her of believing the worse about him but Lorna assures him that she loves him.
In the boiler room, Carney relieves the guard and stands watch. David comes in and asks to take a look around, but clubs the engineer unconscious when his back is turned. He then offers Josiah $5,000 to wreck the Enterprise and kill the boy. The Craggs agree and David starts to unchain them, but Carney manages to sound the alarm. Grey and Bun run in and fight David and the Craggs. They knock out the family but David grabs Carney's gun and warns Grey and Ben that no one will take Lorna from him. He steps back and bumps a release valve, and is scalded to death in a burst of hot steam.
Later, Lorna brings the boy to the pilothouse as the Enterprise approaches St. Louis. As they watch Grey pilot the ship, Lorna sings her husband's sea chantey and the boy hesitantly joins in. She lets him sing on his own and realizes that the boy is Bobby after all, and hugs him in triumph.