It's just a normal day for Courage, who sleeps near the henhouse, where Muriel is collecting eggs. Then a masked woman comes and proceeds to whack the dog with a washbasin. When Muriel comes out from the henhouse, she thinks that the woman is Courage's friend, who is playing with him. She invites her to dinner. During the dinner, the masked woman reveals herself to be "Kitty," and tells Muriel, Eustace, and Courage about her best friend Bunny, who fell in love with a gangster dog and that "all dogs are evil." After dinner, Kitty attacks Courage again, when he is watching TV alone. Muriel sees it, but she believes that they are playing again. Muriel makes a bed for the guest in the garret. At night, Courage spies on Kitty, and sees how she plays with a toy mouse, which is a reminder of Bunny (Courage does not know this). He is convinced that the Mask is evil, and tries to tell it to Muriel and Eustace, but they don't believe him. So, in an attempt to protect them both, Courage locks his owners and Kitty in their rooms, and steals the toy mouse, supposedly as evidence for the police. Then, he drives to the Diner and learns from Charlie the Mouse that Mad Dog has Bunny in his apartment. In the meantime, Courage's owners try to get out of their room, aslike Kitty. Kitty escapes her room, and goes to look for the stolen toy mouse, as assuming that Courage stole it. Courage soons finds Bunny, and saves her from Mad Dog, whom gets involved in a high-speed chase. Mad Dog's car winds up driving on the railroad tracks and is eventually smashed by a powerful diesel powered steam locomotive hauling an Amtrak passenger train. As Courage and Bunny escape, they see Kitty on the same Amtrak passenger train, who pulls Bunny up with her. As the Amtrak train speeds off, the two happy friends thank Courage, and admit that not all the dogs are evil. At the morning, Courage returns home, and Muriel tells him that Eustace now uses the mask (which Kitty left behind at the house in her pursuit) at dangerous work.
- First appearance of Kitty, Bunny, and Mad Dog.
- The second two-parter, after The Tower of Dr. Zalost.
- The situations Bunny encounters in this episode can be connected to real-life situations, notably domestic abuse and prostitution.
- Kitty's mask is an oversized homage to the 80's anime by Osamu Tezuka "Bagi: Monster of Mighty Nature," in which an intelligent genetically modified panther dressed in a trenchcoat and porcelain mask as a disguise while searching Japan seeking her childhood owner, the son of the geneticist who created and killed her mother, and many other modified animals.
- Most scenes of this episode's a parody to the 1988 Walt Disney film, Oliver and Company.
- Although the train in this episode was powered by a steam locomotive, it has an air horn.
- This episode is voted 8th most disturbing in the series for dealing with theme's like domestic abuse, disillusionment, prostitution, and feminism.