The Doctor takes Ruby to a space station in the future orbiting another planet. After discovering a monster in the station's lower decks, the pair discover a crew of talking babies operating the ship in the upper levels. After mistaking the Doctor and Ruby as their parents, the crew explain that they have been alone for six years, under the care of NAN-E, who is discovered to be Jocelyn, the last member of the station's original crew who stayed when the crew were ordered to abandon the station. The Doctor and Ruby investigate the creature, nicknamed the Bogeyman, and learn that it was genetically grown from leftover baby snot, just as the babies were grown by the ship. Jocelyn tries to eject the creature from an airlock but Ruby and the Doctor stop her. Afterwards, the Doctor repairs the station and allows Jocelyn, the babies and the Bogeyman to make their way towards their new home. He invites Ruby to officially accompany him but warns her that he can never take her back to the day of her birth. Instead, Ruby asks to go back to see Carla and Cherry, as the Doctor starts to scan Ruby's DNA.