When the collected works of a famous local artist is announced to be shown at the Langley Falls art museum, Francine admits that she modeled for him. The family takes a trip to the museum, but an otherwise bored Stan becomes dismayed when he finds that a painting of Francine's genitalia is the hit of the show. After being ribbed by his co-workers, he confronts Francine over the work, angering her, and she storms off.
Unable to think of any good options on his own, Stan hooks up with an art theft persona of Roger's. They engage a top-of-the-line crew, but when they almost have the painting, they find that Roger's payment has bounced and they set off the fire extinguisher in disgust. The next day, Francine considers requesting the painting being removed, but finds that it actually inspires people of all ages, so she holds her request. Meanwhile, Stan dons a fake mustache in an attempt to be hired and steal the painting from the inside. As the museum's night watchman was injured in the previous theft attempt, Stan is hired to replace him. Stan successfully steals the painting but is convinced by Roger to sell it to the family cocaine dealer. Francine's discovery of the plan convinces Stan that he may have acted too hastily and returns it to the museum where it is admired by the museum patrons.
Meanwhile, having seen his mom's genitalia has taken the desire to masturbate out of Steve. He dedicates his time to helping others, including getting Klaus a tank filter to help keep his bowl clean. A side effect of his discontinuing masturbation is his deepening voice, which is noticed by Principal Lewis who also runs an aquarium shop. His advice regarding an unfamiliar filter leads Steve to get more information. However, he finds his conversion with the female phone rep returns his desire to masturbate during the call. Afterward, Steve has returned to his old self with his normal voice and no desire to help Klaus.