The Doctor and Rose are following an object that is in the time vortex and is heading for London. When they arrive, about a month later, the Doctor tries to get its location by questioning people in a pub. Rose, meanwhile, following a small child's cries for help, is accidentally stranded holding the mooring rope of a barrage balloon. When she falls, she is saved by a seemingly American soldier in a space ship with a tractor beam. The Doctor, leaving the pub when an air raid is sounded, hears the telephone on the TARDIS ring. He is warned by a young girl not to answer and when he does hears a small child asking for his mummy. He follows the girl to a house that she has broken into and is feeding homeless children from. He learns a little more about this child from the girl, Nancy, just before he attempts to get in the house. He appears to be wearing a gas mask and can use electronic equipment to send his "are you my mummy" signal. Rose learns that her rescuer, Captain Jack Harkness, is a rogue time agent from the future and is trying to sell the artifact she and the Doctor tracked. The Doctor finds a hospital that should hold the answers to his questions. He finds many people there apparently dead, all with the same wounds. The overseeing doctor succumbs to the "disease" and the Doctor watches as he grows a gas mask around his face. When Rose and Captain Jack arrive, the dead people rise and start to close in on them.