In 1813, Lord Barton is walking with some other upper class guy. They seem to be flirting but when the other guy suggests Barton needs to marry a woman, Barton grabs him. Lightning flashes and we see women's shoes. The man is killed.

After the intro, the Doctor and Ruby are at the Duchess' Regecy ball. Ruby is thrilled to be experiencing this. It's her dream come true. The Doctor explains she knows the dances because her earrings are psychic.

They are interrupted by the Duchess, who doesn't recognize them. Ruby introduces herself as Lady Ruby Sunday of Notting Hill. The Duchess wants her to meet a suitor. Ruby's psychic earrings go crazy but the Doctor tells her to go have fun and he'll handle it.

Barton approaches Ruby who is rude to him when she doesn't appreciate his flirting. Ruby walks off.

Meanwhile, the Doctor meets Rogue on the balcony and tries to find out why he is watching the party from up here. There is a flirtatious vibe. Rogue tells the Doctor to meet him outside.

Ruby sees a portrait (Susan Twist again) and asks who it is. It's the Duke's late grandmother. The Duchess sees something she doesn't like and tells Ruby to wait here.

The Duchess goes outside. She is rude to Lady Wallace about wearing a dress she wore before. She sees her housekeeper and tells her to go inside. THe housekeeper grabs her and turns into an alien. She whispers she will take the Duchess' form now and lightning strikes.

Ruby spies on Barton and Lady Emily Bennett, who are having an affair It's like watching Bridgerton, until Ruby accidentally drops a book and Barton goes. Emily is upset but Ruby tells her that Barton is not worth it and shouldn't be putting his lifestyle over true love (how much history is she changing here?)

THe Doctor and Rogue find the Duchess' body and Rogue concludes the Doctor is the shapeshifter that killed her and pulls out a gun.

Ruby and Emily go dancing and have fun. Meanwhile, Barton complains he wanted to turn into the Duchess and his alien partner says she plans to go to the wedding as Ruby.

Rogue takes the Doctor to a ship. The inside looks like a messy version of the TARDIS. Rogue decides he is going to execute the Doctor. The Doctor fools around with his sonic screwdriver, turning on dance music and aggravating Rogue as well as flirting with him.

But seriously, Rogue won't listen and wants to kill the Doctor. He says his scan shows the Doctor is a shapeshifter.

The Doctor tosses his psychic paper and turns on the scanner, which then displays holograms of every one of his previous incarnations. Rogue realizes he made a mistake at the last second.

The Doctor takes Rogue to his TARDIS and while setting a trap, they chat. Rogue has lost someone too. The Doctor says we must go on because they can't.

The Doctor wants Rogue to join him in the TARDIS. Rogue wants the Doctor to join him in his ship. They almost kiss but a chime tells them the trap is ready.

The Doctor and Rogue need to lure the fake Duchess outside. They decide to set a trap by showing off their gay relationship in 1813. Rogue proposes and the Doctor says he can't and walks off.

Outside it turns out there are four shapeshifters and the Doctor and Rogue run.

Emily seems upset and runs off.

The Doctor adjusts the trap but they only have one chance to get up to six monsters.

Emily reveals herself to be a shapeshifter and grabs Ruby. Ruby screams.

The Doctor is concerned he can't find Ruby. The shapeshifters walk in in their true form, and it is revealed one has taken Ruby's form.

The Doctor, upset, goes upstairs and finds Ruby's body. He cries and remembers promising Carla he'll keep Ruby safe. Rogue says the shapeshifters can live 600 years. The Doctor vows they will suffer all that time.

The trap is set as the wedding begins. But after everyone is trapped in the transport gate, Ruby reveals that she is herself! She set the psychic earrings to battle mode and defeated the monster. She can't move and the Doctor can't turn off the trap.

Rogue shows up. He tries to convince the Doctor to sacrifice Ruby so the monsters don't destroy the world. The Doctor can't. Rogue kisses him and then pushes Ruby out of the way and takes her place before engaging the transport.

It's over. All that's left of him is his ring. The Doctor is upset.

The Doctor and Ruby sit outside later. The Doctor tells Ruby he sent Rogue's ship into the orbit of the moon to wait for Rogue's return. Ruby thinks they can use the TARDIS to find Rogue but the Doctor says that's not possible. Too many possible dimensions for him to have gotten to.

The Doctor puts on a happy face and says anyway onward to the next adventure. Ruby tells him he doesn't have to do that. He says this is who he is. Ruby hugs him. He's glad to have her back. 

As Ruby goes into the TARDIS, the Doctor puts on Rogue's ring and salutes his ship.