Private Lessons

Philip "Philly" Fillmore (Eric Brown) is the 15-year-old son of a rich widowed and sexualy active businessman in Albuquerque who has left town on an extended summer "business" trip, leaving the young man in the passing care of Nicole Mallow (Sylvia Kristel), a sexy French housekeeper, and Lester Lewis (Howard Hesseman), the family's chauffeur.Philly becomes infatuated with Nicole. One evening, when she spots him peeping into her room, she tells him to close her door. To Philly's utter shock, she means for him to close her door from the inside and then watch her undress. However, it is too much for him when a topless Nicole asks him to touch her breasts. When he objects, she steps back and instead takes off her underwear. Philly panics and leaves.Later on, he is surprised to find her in his father's bathtub. Once again to his amazement, she asks him to join her. He objects, but she keeps sweet-talking him until he finally gives in. However, he decides to wear boxer shorts. Once in the bathtub, she spoons and kisses him from behind. When she tries to take off his boxers from behind, he insists that she off the lights first. But once she reaches for his private area, he again panics and rushes out. She follows him to apologize, kisses him and directly invites him to sleep with her, the sexual element of which he fails to comprehend at first.After they flirt in a movie theater the following day, he gives in but backs down when she reacts without fondness to the notion of marrying him. One day later, she tells him she guesses they can at least date for a while. After they flirt during their first date in a restaurant, they return home and have sex.Nicole is revealed as an illegal immigrant; Lester is using this secret to blackmail her into helping him in a larger blackmail scheme against Philly to swindle him out of his inheritence. Lester intends that Nicole seduce Philly then fake her own death during intercourse. Lester then "helps" the panicked Philly to secretly bury Nicole. Her body later disappears, and a note orders Philly to steal $10,000 from his father's bank account to prevent exposure of his role in Nicole's "death".When Nicole has second thoughts, Lester threatens to also expose her as a child molester. Nicole has truly fallen in love with Philly, and she reveals the truth to him. Philly decides to get back at Lester by convincing his school tennis coach (Ed Begley, Jr.) to pose as a police detective and intimidate Lester with questions about Nicole's disappearance. Lester panics but is caught with the money before he can flee the country. Nicole and Philly return the money to the safe, but they decide not to expose Lester's treachery. In turn, he reluctantly decides not to expose Nicole's illegal alien status nor her acts of child molestation, and as a result, he keeps his job.Nicole fears that Philly's father will eventually discover their affair, and decides to leave. Before she does, she and Philly have sex one last time. A few weeks later, summer comes to an end. Philly returns to high school. In homeroom class he thanks his teacher for advising him to pursue girls whose age is more appropriate for him, and successfully asks her out to dinner.

Question: Who poses as a police detective?
Answer: Philly's tennis coach