Herman the cat approaches Libby when a new man in the neighborhood looks just like a man he shot dead in his human life as a mob hitman. Turns out it’s the son of the deceased mobster, whose dementia-afflicted mother steals small items from neighbors. She’s especially fond of taking the tub full of garden tools from Norman, Mama’s new neighbor. And when the son returns the tub one day and introduces himself to Norman, Libby notices Norman looking at the friendly visitor strangely.

Since Norman visits Mama every day, he tells her about the young man and claims he looks like a mobster’s son he encountered during his days as a New York policeman. He says the son didn’t like killing people, so he turned state’s evidence and went into the witness protection program. Norman is concerned about the young man, but tells Mama not to worry.

When Norman goes missing and the police show up looking for him, the pets know something wicked is afoot. Herman peeks into Norman’s trailer to make sure he’s not dead, but finds it’s barely furnished with a cot, a card table, and a folding chair. With their suspicions aroused, Percy sends Herman down to 352, where the young man and his mother live, and the news he returns with is not good. It’s an especially heavy burden for Herbert, given his history with the family.

Percy, Gigi, and Herman arrange to alert the police about 352, and soon Mama and Mrs. Beebee see Norman on the news. His real name is Ralph Malloy and he’s long been linked to a crime family. But Herbert returns with another problem: he heard a human voice coming from Norman’s trailer, and it turns out a tiny black kitten is trapped in the hot building without food or water. Herman feels especially driven to save the kitten, eager to atone for his felonious past, so the pets mount a mission to rescue her. While participating, Libby has a flashback to her death as Percy in World War I, which frightens her badly, but she pushes through her fear to help Herman drag the kitten to safety. Not that the small feline is grateful: when Connie comes by to tell Mama and Mrs. Beebee that she’s found the little black cat a home, although she doesn’t seem to like dogs, the cat quips “You got that right, sister.”

But the real surprise is yet to come. As the new residents of Norman’s trailer move in, Libby hears a young male voice screaming in terror, begging for help, then peeks out the window to see a cute chihuahua sitting opposite her. New neighbors …