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. Over dinner, Diana notices a certain gentlemen friend, with whom she has an "understanding", dining intimately with another woman.

Meanwhile at the party, Molly's cool school friends and Alex's geeky ones, in fancy dress as their favourite Crustaceans, don't quite mix.

Back at the restaurant, as Diana looks daggers at the two-timing Laurence, Jimmy is still trying to digest the shock and amusement that she has a secret love life. However, seeing how genuinely humiliated Diana is, Jimmy gallantly steps into the breach by pretending to be her bit-of-rough.