After being stranded on Carpathia by the Cravat Doctor, the Rani must try and make her way through the universe, but she attracts the attention of an entirely different Doctor along the way.
Having found a disturbance in the timeline, the Tenth Doctor arrives on a planet where the Daleks own their largest slave camp. An experiment is being undertaken, one that will need the assistance of two Doctors to stop.
Having received a signal that Charley is in danger, the Blonde Doctor goes to help. However, it's the wrong Charley. Coming face to face with the Eighth Doctor who's looking for Charlotte Pollard, they embark on the journey to save her.