Joe has finally found true love with the beautiful Alice Harper. The two have a wonderful courtship and very soon, they are engaged. Unlike past relationships the Cartwright brothers have had, this time, Joe makes it to the altar.
All appears well, as Joe and Alice start their new life together in their new home until one day when Joe is out. Alice's shiftless brother, John Harper, has not paid his gambling debts, and Damien, a proper and ruthless gambler, is running short of patience. Mr. Hanley, his hired thug, beats up John. It becomes clear to Damien that he is unable to make good on the debt. Cornered, John blurts out that Alice has money. After all, she married into one of the wealthiest families in the area, and they have lots of money to spare. So, Damien and his henchmen saddle up and ride to Joe and Alice's home.
Meanwhile, Joe and Alice's budding young marriage continues to blossom. The youngest Cartwright, according to Ben, is working harder than he ever did on the Ponderosa; he's got a house, a beautiful wife, and he's going to be a father.
Joe is working on an addition to his home, a perfect room for that cradle he had also built with his two hands. Needing more lumber, Joe tells Alice he's going to stop by home. Alice tells Joe that everyone is welcome for supper. As he's leaving, Joe yells back to his wife, "I love you!"
Zoom in on Damien and his gang, John held at gunpoint, waiting in the bushes for Joe to leave. The bad guys break into the house and demand Alice re-pay her brother's debt. Alice refuses, and Damien is quite displeased. Sloan, one of Damien's henchmen, re-enters the room with the music box Joe gave Alice, and Damien decides it would be a perfect way to repay the debt; after all, hocking it in a nearby city where no one could track it down, he'd have the debt repaid. Alice protests his taking of the box. John lunges at Damien who, fast on the draw, shoots and kills him .
As Damien asks once more for the box, Alice uses the opportunity to try to escape through the bedroom window. Before she can make her getaway, Mr. Hanley, breaks into the bedroom. Alice's worried expression turns to fright and fear as Damien menacingly and murderously stalks her.
Back at the Ponderosa, Joe and Candy are loading the buckboard full of lumber and decide they need to finish off that pie that Hop Sing baked (so as not to offend him). Late that afternoon, Joe, Candy and Jamie happily ride back to the Cartwright home, anticipating a wonderful dinner and a memorable evening, until Joe sees burning structure in the distance.
Joe hurries back to the homestead see his worst nightmare come true: his house engulfed in flames and Alice nowhere to be found. Joe runs to the burning house, hoping to find an open window to save Alice, and despite the searing heat, continues to try to get in, screaming all the while for his beloved wife. Candy has to repeatedly tackle Joe and eventually drags him away.
Later that night, after the fire has been extinguished, Doc Martin has taped up Joe's burned hands and sedated him. He gives Ben the medicine for safekeeping, concerned that a deeply grieving Joe might try to overdose if he got his hands on it; Candy and Jamie look at each other with concern. Meanwhile, Deputy Clem and his posse search the house for the fire's cause and find Alice's charred remains.
The next day, Ben rummages through the still smoldering remains and opens the door to the stove where he believes the fire started. His suspicions are confirmed when Clem says the fire was no doubt arson, especially since it was a very hot fire. The deputy also remarks it won't be necessary to contact John, showing him the singed ring inscribed with the initials J.H. "Why, Clem, why?" ponders Ben, knowing that his youngest son's entire life, vision of happiness and joy has gone up in smoke. Clem, initially at a loss for words (and perhaps remembering his own fiance's fiery death two years earlier), sadly replies, "God only knows. God only knows," as he slowly walks away.
After an emotional graveside service, Joe rides back to his house, now a smoldering pile of rubble. After walking through the ruins, Ben shows up to ask Joe to come back home. Joe tearfully insists he is home, but later really breaks down and cries. A rarely emotional Ben also breaks down, and the two embrace in an heartbreaking moment.
Later, Joe decides he needs to spend some time away and, after bidding his father farewell, leaves. Shortly after walking out of the room, Ben caresses a picture on Joe's dresser and leaves the room. Zoom in, and we see the picture he had touched lovingly was Hoss. (No mention is made as to why, but we can presume with Dan Blocker's death a few months earlier, that Hoss, too, had died).
After riding to visit his beloved Alice's grave, Joe spends several days drifting. (There's a shot of Joe looking over the countryside as the camera pans across the scenic Nevada mountains, and a mournful,lonely score plays.)
Late one night, Joe, having essentially become a drifter, his appearance having become haggard, stops at a small-town hotel for a drink of whiskey and to rest before another day riding alone. Just before he enters the hotel room, he hears a music box from another hotel room, and it's playing a strangely familiar tune.
In fact, this music box is playing the very same tune as the one Joe gave Alice. In fact, this is THE very same music box.
Joe bursts in and a couple is seated inside, listening to the melody. He demands the young man to tell where it came from, but he won't tell and Joe tosses him out. He turns to the woman, a stage actress, and barks at her to start talking. Not until he grabs her chin does she reveal that a man named Damien gave it to her, and he was with three unidentified men. They had all been in town for several days, running the locals bankrupt with their gambling. She tells Joe that, after a night of gambling and heavy drinking, they were possibly headed to San Francisco.
After a close-up of the music box, we pan over to Joe, who has returned to the Ponderosa, albeit briefly, to get Candy and load up on the ammunition and supplies. Jamie wants to come, but Joe tells him to ride to Virginia City instead to alert the authorities and pawn shops in San Francisco in case they try to sell Alice's diamond pendant that Joe had given her.
During a brief stop in a small town, Joe sees a young family walking around, complete with a beautiful young boy; the family is laughing and enjoying the time watching the toddler learn to walk. Joe hears Alice's voice echo in his head, and he wonders what might have been.
Meanwhile, Sloan complains about being stuck in a small town. Damien, demanding total obedience and loyalty from his henchmen, asks Mr. Hanley to show Sloan the error of his ways, forcing him to beg for forgiveness. Damien pours a bit of his wine on Sloan's head, and then drinks from the chalice.
Early the next morning, well before sunrise, Damien's lackeys see torches in the far distance, and Damien senses that they are perhaps being followed by a posse. It's decided they will split up temporarily. While two of the thugs stay behind to ambush whoever is coming for them, Damien and Mr. Hanley will ride to restock on fresh water.
Joe and Candy soon ride into the area where two of the henchmen are waiting in the bushes. Thanks to a soft whinny from one of the horses, the two anticipate they will be shot at and, at the right moment, ride off in separate directions, barely avoiding gunfire. Joe and Candy quickly defeat Sloan and Krater, the latter getting killed and Sloan wounded; Candy is also grazed in the arm by Krater's bullet. Sloan quickly blabs about Damien's whereabouts, that he was just at the Cartwright home and never laid a hand on anyone, and that Hanley was the one who used his two hands to administer the brutally fatal beating to Alice before Damien set the house on fire. Candy stays behind until the posse is able to take the crony into custody. An angry Joe rides to take care of Damien and Hanley.
After Joe tells who he is and accuses Damien of killing his wife, Damien questions why he is even being fingered. After all, any evidence would have been been burned and there were no eyewitnesses. Joe says he was able to link the music box to Damien.
Damien nonchalantly downplays what he considers a simple faux pas. Then, since there is no judge or jury nearby to listen to the evidence, he demands an impromptu fight between Joe and Hanley. He orders his brute to kill Joe, but the Littlest Cartwright is able to defeat the gigantic thug.
Joe picks up a huge boulder and ponders for a moment, but then relents. Killing Hanley, after all, would give Damien too much satisfaction. Damien, twice ordering Joe to deliver the fatal blow; each time, Joe refuses.
Then, Hanley grabs Damien from behind and throws him in the river. Damien is able to fire his rifle, the force of the shot knocking down Joe but not injuring him.
An angry Hanley stalks Damien in the river. Damien begs Hanley off and runs into the nearby river, but Hanley grabs the villain -- perhaps in revenge for years of being bullied, or maybe because Damien had demanded his death –- he breaks Damien's neck and drowns him.
In the coda, Joe bids Alice one final farewell. We pan one last time across the beautiful meadow and Nevada timber, into the glistening river...and fade out.