On Christmas Eve, the Doctor and Clara decide to go to a masquerade ball in New York City in the 1980's. They're both a bit insecure when it comes to a 'date', but it's not at all what they had expected. There, they tell stories and reveal somethings they weren't planning to in the first place. Alongside that, a song comes on and starts a conversation between the two of them; a conversation that changes both of them on the inside, strengthens their friendship, and gets them partially ready for what's about to come. For the Doctor, it's what's about to come in the next few centuries.