Manacek is a detective from the 1970s. He makes his first appearance in "Homer Is Where the Art Isn't".
At Gavelby's Auction House, Homer and Mr. Burns lose to Megan Matheson at bidding for Joan Miró's painting The Poetess, which Homer is obsessed with. As soon as the painting arrives at her home, Megan finds out that it has been stolen. Detective Manacek is promoted to solve the case.
Manacek goes to Megan's estate due to insuring the painting for doubling the price she paid of thirty million dollars. Megan denies the accusation and sends Manacek to Burns' mansion. Manacek proclaims that he can't stand of losing a bid to a woman, but also dismisses the accusation and Megan sends Manacek to expose the last suspect as Homer due to the obsession he showed about it. Homer demonstrates to him how much he wants the painting at the Power Plant. That evening, Marge goes to Manacek's apartment, Brick Townhomes to convince him that Homer is innocent, but he says they would only talk at dinner. So Marge invites him to the Simpson house.
After dinner, Homer becomes worried when the pair starts talking, and Bart and Marge explain how Homer becomes attracred to the painting at the Springfield Museum of Fine Arts, even dreaming about it at night. When the museum closed due to being out of funds, Springfielders protested while Mayor Quimby realized the cuts, including the cut of 1/3 of the Springfield Police Department with Eddie having been fired.
The scene returns to the start of the episode where the bids took place, and Homer tries to steal the painting. After the story, Homer takes off, but Manacek finds him at the museum where he tells Homer that he is innocent because he finds the latter positively stupid to steal anything. Manacek then reveals that Megan was in fact the culprit, having exchanged the security guards by twins hired by her, to simulate the heist. Manacek then reveals it was already stolen by Burns when he built an identical auction house next to the original one and stole it from the vault.
After Burns was arrested at his mansion along with Megan, Manacek reveals that the painting is nothing other than Lisa's book bag, so it wouldn't go to millionaires' houses hidden away from people who loves them, like Homer. At the end, the painting is located at the Springfield Arena Football Arena, built with the money from selling the public arts.
During the credits of the episode, there are different shots of Manacek as if they are part of a crime drama TV show.