After You've Gone - Season 1 Episode 2 Silence Of The Clams

Jimmy overcompensates for his previous failings as a father by letting his kids throw a party. Knowing Diana would completely disapprove of this, Jimmy agrees not to tell her and keep her away from the house on party night. Under the pretext of seeking advice on matters "too personal" to discuss around the kids, he invites her to dinner. At Diana's favourite restaurant, Jimmy discovers that while he and the kids have been sneaking around behind Diana's back, Diana has been sneaking around theirs.