Tom challenges Josh and Claire to smash his piñata, which is full of secrets from their past. While Arnold is away at a maths summit, Josh decides to test out the idea of their "open relationship", and before he's had time to change his mind, he's hosting a random hookup with a smart but decidedly odd guy called Ben. Claire gets stuck with Tom in his room while they stay out of Josh's way and wait for Ben to leave. After an awkward start, the two revive their friendship by playing an epic game of Penis or Not Penis. Meanwhile, Josh is unexpectedly challenged and intrigued by Ben.