A piano teacher from a highly dysfunctional family must finally face the music when she becomes involved with one of her students in “Mustang Sally.” The teacher, Kathy (Sally Conway), is unaware that her illegal behavior is in any way reprehensible or amoral. She insists that she’s in love with her 13-year-old paramour.

She tells her sister, Elizabeth (Andrea Conte), about the affair. Elizabeth goes ballistic and immediately rushes in and takes charge of the situation, which includes contacting her boring attorney friend, Edward (Michael Blain-Rozgay) to handle the details.

Kathy’s colleague and local art teacher, Tony (Sean Vincent Biggins), doles out exposition from the school’s perspective. He updates Kathy and her friends with news from the principal, the faculty and the students. He even has news from Kathy’s lover, 13-year-old Salvatore.

The situation is further complicated by Kathy and Elizabeth’s flakier than phyllo dough mother, Marilyn (Tish Smiley), who is an irascible jangle of inconsistencies – filled with equal parts greed and tenacity. She isn’t a likely candidate for mother of the year, but Smiley’s performance is the highlight of this slim, mediocre production.

Playwright Linda Felton Steinbaum experiments with some controversial issues in “Mustang Sally,” but the play never realizes its full potential. The characters are watered down and tepid. Conte and Smiley are powerful actors and overshadow the talents of the other actors.

The Whitefire Theatre is a gorgeous little acting space in the valley, but “Mustang Sally” is hardly worth the ride.

The Whitefire Theatre is located at 13500 Ventura Boulevard in Sherman Oaks. Show times: Fri & Sat, 8 p.m.; Sun, 2:30 p.m. Tickets: $20. For more information, visit www.mustangsallytheplay.com.