Lucy is busy changing the water of Mildred and Charles, Little Ricky's two goldfish. Ethel comes in and Lucy declines an invitation to go with her to the market so she can take care of Little Ricky's other pets: two parakeets (Alice and Phil), two turtles (Tommy and Jimmy), and a frog (Hopalong). Ethel asks why Lucy allows Little Ricky to keep all those pets. Lucy explains that she thinks a child should have pets, and confides in Ethel that she wants to move to the country so Little Ricky can have all the animals he wants. Ethel objects to even the possibility of the Ricardos moving due to their strong friendship. Ethel also mentions that she and Fred have been having quite a time with the apartment next door. It's finally been rented to a grouchy tenant, Mr. Stuart.
Later, Little Ricky comes home with a puppy in his arms. He says he got it from his friend Billy Palmer, whose dog just had six puppies. Lucy tells him that he won't be able to keep it. She takes the puppy from Little Ricky and calls Billy's mother to tell her that they can't keep the puppy, but she instantly bonds with him after he licks his face. When Ricky gets home, Lucy tells him that Little Ricky now has a puppy. Ricky explains that Little Ricky can't keep the dog and suggests that Lucy should've handled the situation firmly. He goes to tell Little Ricky that he can't keep the dog. He goes into a spiel about Little Ricky not being able to have everything he wants. A few moments later, however, he emerges from Little Ricky's room to go to the basement to look for a box for the puppy. As he opens the door, the Mertzes arrive to discuss Little Ricky's dog. Fred reminds the Ricardos that there's a "no pet" clause in their lease. Fred refuses to budge, reasoning that everyone in the building will want a dog if Little Ricky's allowed to keep his. Little Ricky enters with his puppy and announces that he will call him after Fred, who, as a result, soon changes his mind. He goes downstairs to the basement to get the box.
That night, the Ricardos are awakened by the dog's barking. Fred calls and tells Lucy that he's gotten six complaints from the other tenants. Lucy gets up and ends up quieting the dog with a ticking alarm clock and all is peaceful again--until the alarm clock goes off, and wakes up the dog. He begins barking and Ricky and Lucy go to calm the dog down. Fred and Ethel arrive (courtesy of Fred's banging at the door) and alerts the Ricardos that Mr. Stuart has threatened to move. The Mertzes leave and the Ricardos try figuring out who will tell Little Ricky that the dog has to go. Ricky suggests that the one who sees Little Ricky first should be the one to tell him the bad news.
The next day, Ricky awakens and sees that "Lucy" is still asleep. He gets out of bed, fixes it to make appear he's still asleep in it, creeps to the bathroom to get dressed. Lucy peeks her head out to see if the coast is clear. She sees that "Ricky" is still asleep and goes to the kitchen. By now, Ricky has gotten dressed and creeps outside the apartment. Shortly after, Lucy comes from the kitchen and goes into the apartment. The two come back into the apartment to demand that the other give an account of herself/himself. Ricky explains that he is on his way to rehearsal, while Lucy alleges that she's on her way to the market. Both realize how ridiculous the excuses sound since it is only 7:00 in the morning. It is also obvious to Ricky and Lucy that the other was trying to avoid telling Little Ricky that the dog cannot stay. Ricky decides that he should be the one to tell Little Ricky the bad news, but upon seeing Little Ricky holding his Fred, Ricky chickens out and tells Little Ricky that his mother has something to tell him and then dashes out of the apartment. Lucy again tries telling Little Ricky that he can't keep the dog, but procrastinates and goes to fix breakfast for Little Ricky.
Later that afternoon, Lucy and Little Ricky are sitting on the couch and playing with puppy Fred when there's a knock on the door (he's in one of Lucy's hats). It's Fred asking Lucy whether she got rid of the dog. She dodges the question, and Fred explains that Mr. Stuart wants to see for himself since he's been hearing the dog's barking. Lucy sends Little Ricky to take a nap and hides the dog in the closet. She opens the door and lets Fred and Mr. Stuart in. Taking a look around the apartment, Mr. Stuart asks Lucy whether there's a dog in the apartment. In spite of Lucy and Fred's assurances, Mr. Stuart has doubts and threatens to take back his first and last month's rent and move out if he finds a dog in the apartment. In spite of repeated assurances that there isn't a dog in the Ricardos' apartment, Mr. Stuart has doubts--especially once he sees dog biscuits on the coffee table. Lucy lies and says that they're hers and begins eating one. Ricky enters and apologizes to Mr. Stuart about the dog's making noises the previous night and assures him that they've gotten rid of the dog. Ricky goes to the closet to hang up his coat, but Lucy quickly offers. She hangs up the coat, but doesn't securely close the door, and Fred walks out of the closet concealed beneath the hat. Fred explains to Ricky that Mr. Stuart is having his kitchen remodeled and wants to see the Ricardos' kitchen. Lucy encourages Ricky to go ahead and show Mr. Stuart their kitchen, but he notices the hat and asks what's going on. Lucy explains that she's practicing a hat dance and begins dancing. The men go into the kitchen, leaving Lucy to follow the puppy. Puppy Fred ends up going out of the apartment, so she goes after him and brings him back to the apartment--just as Mr. Stuart, Ricky and Fred are coming out of the kitchen. She quickly places him inside the piano. The puppy begins barking and moving inside the piano. Lucy tries convincing the men that she's playing the piano and taking singing lessons. Little Ricky comes in and asks where his dog is. Ricky takes the dog out of the piano and hands him to Little Ricky. With the jig up, Mr. Stuart announces that he's moving. Fred reminds Mr. Stuart about his lease. Mr. Stuart, in turn, reminds Fred about the "no pet" clause and gives him an ultimatum--either the dog goes or he goes. Fred tells him that he would rather stay with a little dog than a big grouch. He hands Mr. Stuart back his check and tells him to leave. Ethel comes in as Mr. Stuart leaves. The Ricardos explain what happened. When Ethel brings up how much money they've lost with Mr. Stuart moving out, Fred gets light-headed and faints.