Society-lawyer Warner Baxter loses his prestige in the legal community when he successfully defends gangster boss Nat Pendleton. Later on, the soft-hearted Pendleton gets the opportunity to "do right" by saving Baxter's life. This redemptive move comes at the end of a complicated plot involving Baxter's efforts to save Phillips Holmes, who has been framed by nasty mobster C. Henry Gordon, from the hot seat. He is aided in this effort by Gordon's former mistress Myrna Loy, who has all of the film's best lines (When her protecter Baxter falls asleep on a couch, Loy complains "A few more nights like this and I'll be out of condition.") Also in the cast of Penthouse is crime-movie perennial Mae Clarke, here cast as the murder victim. Penthouse was later remade (and highly sanitized in the process) as Society Lawyer, with Walter Pidgeon in the Warner Baxter part.
by Hal Erickson synopsis