All of the Cunninghams are at house, and they notice that they have taken somebody else's groceries. Fonzie comes rushing in and says that somebody has been following him. Somebody knocks at the door, and Fonzie answers it. The man asks if he is Arthur Fonzarelli. Fonzie says "no" and slams the door in his face. The man knocks at the door again. Fonzie opens the door. The man has something really important to tell to Fonzie. Fonzie asks what it is, and the man says that he is his brother. Fonzie slams the door in his face again. He thinks that the man behind the door is a con artist because he (Fonzie) doesn't have a brother. The man opens the door by himself and tries to explain to Fonzie that he is really his brother. Fonzie doesn't believe him, and he leaves through the kitchen door. Fonzie's brother starts to sing a song, and Fonzie comes back inside and starts to sing, as well. After that, Fonzie believes him because only a Fonzarelli knows that song. Fonzie is excited and asks what the man's name is. His name, also, is Arthur, but he is called "Artie." Joanie comes down from upstairs and takes a picture of the two of them.
Chachi is playing at Arnold's, and everybody is dancing. Fonzie and Artie come in. Fonzie introduces Artie to Chachi. Chachi goes to the kitchen to make burgers for Fonzie and Artie. Marlene and Darlene Lovejoy arrive at Arnold's. They are Fonzie and Artie's dates. Chachi brings them the burgers and goes back to the kitchen. After a little while, Marlene and Darlene go to freshen up. Artie wants to tell Fonzie something about their father, but Fonzie doesn't want to hear it. Marlene and Darlene come back from the ladies room, and they are arguing about who gets to be with Fonzie. Marlene and Darlene leave Arnold's.
Howard comes downstairs in the middle of the night and wonders what the noise is. Fonzie is making a milkshake. As they drink their milkshakes, they discuss Fonzie's brother. Fonzie says that he hates Artie.
Fonzie explains to Howard that he has no feelings for his brother whatsoever. Artie comes to the kitchen, and Howard goes back upstairs. Artie tells Fonzie that he is going back home. First, he wants to tell him something about their father. Artie says that he died two weeks ago, and he gives Fonzie their father's old watch. Fonzie doesn't want it. Artie leaves the house.
Howard goes to the bathroom in the middle of the night and almost has a heart attack when Fonzie emerges from a dark corner. Howard asks what he is doing there. Marion and Joanie wake up and wonder what's going on in the bathroom. Fonzie explains that he wanted to talk to one of the Cunninghams. He figured that, eventually, one of them would come to the bathroom. He says to the Cunninghams that his father died. They talk about it. Fonzie says he wanted to know some things about his father. Howard says that he should talk about these things with his brother. Fonzie leaves the bathroom.
Fonzie talks with Artie about their father. Artie gives their dad's watch to Fonzie. Artie leaves to board the plane but turns back. Artie asks what Fonzie is doing for Christmas, and Fonzie says that he'll be decorating the Christmas tree with his brother. They hug, and Artie leaves. Fonzie reads an inscription on the watch from his father.
Fonzie arrives at Arnold's and goes to the table where Chachi and Joanie are. He shows them his watch. Fonzie notices that the watch is broken. Fonzie snaps his fingers, and Marlene and Darlene come to him. They leave Arnold's together.
Songs in this episode:
"Heat Wave" (instrumental) by Martha And The Vandellas (1963)
an unknown instrumental
"What'd I Say" (instrumental) by Ray Charles (1959)
"My Girl" by The Temptations (1965)