Mac Bookpro (Peter Griffin), a “Private Dick,” has just solved a case involving the unfaithful wife of Seamus in a 1940s film noir adaptation of Quahog. Soon later, Heddy Toothbrace (Lois Griffin) welcomes him and requests that he look into the disappearance of her daughter, Sister Megan (Meg Griffin). Mac looks in several different areas and begins to suspect Cardinal St. Louis (Carter Pewterschmidt), but after nearly being attacked by Bogey (Mort Goldman) and Bacaw (Ernie the Giant Chicken), he learns of Megan’s shooting death. In her remains, he finds a roll of film. He takes Heddy on a date while the movie is in production. Pictures show that Heddy and the Cardinal are working together with the mafia. Karol (Chris Griffin), a less-important mob member, supports this claim by disclosing his aspirations to corner the market for alcohol and his underground alcohol company. When Mac goes to the church to confront the Cardinal, he discovers that he has been fatally stabbed.
When Officer Ace Hardware (played by Joe Swanson) arrives, he claims that the bullet in Megan matches the ones in Mac’s gun and that the murder was a setup to put Mac in jail. Heddy admits that she is innocent and was simply running away from the town for her own protection as Mac pursues her to the harbor after receiving bail from newspaper reporter Red Weiner (Brian Griffin). Fanny Patbottom (Stewie Griffin), Mac’s transgender assistant, exposes himself to be a previous orphan Megan molested when the Cardinal was preoccupied with his bootlegging. He prepares to shoot Mac with his own gun as he plans to exact revenge on everyone who has wronged him, but Seamus knocks him down, and Hardware and the police take him into custody. After the lawsuit is concluded, Mac and Heddy get ready to wed in Hawaii, and Fanny is brought to the asylum where she will undergo lobotomy and castration.