The Doctor picks up a distress signal and is drawn back to Earth in the year 2012. The Tardis lands in an underground bunker in Utah, USA. Stepping out of the Tardis, the Doctor and Rose discover they are in a museum of alien artefacts. They find a Slitheen arm and one of the Doctor's old 'friends'; a Cybermen. But it's just a dormant helmet, and not the source of the distress call. When the Doctor touches the glass, alarms are sounded and the two are soon apprehended by armed security.
Henry van Statten is one of the richest, and most eccentric men in the world. He will acquire any alien artefact he can get his hands on, no matter the price. His orders are never challenged, if they are, the person is immediately dismissed, has his memory wiped, and dropped off in some random city. When he hears about the Doctor and Rose he tells Diana Goddard and the rest of his group they must have come "intruder" window. A joke no thinks is funny till he tells them it is.
Van Statten's most prized possession is a live alien specimen he calls the Metaltron. Though he knows it's capable of speech, the Metaltron has yet to talk to Henry, so he has one of his men torture it. When the Doctor boasts about his knowledge of alien technology, Henry offers to show him the Metaltron.
The Doctor is led into a darkened room. The door closes behind him by order of van Statten. A single light is illuminated and the Doctor reassures the creature he is there to help. But this alerts the Metaltron and the rooms lights are illuminated. This is when the Doctor first realizes the Metaltron is in fact a Dalek. The Dalek tries to exterminate the Doctor but it's gun in inoperable. The Doctor laughs and tells the Dalek how worthless he is, especially since he's the last Dalek in existence. We then learn the Doctor had to sacrifice his planet in order to destroy every Dalek in a "Time War".
When the Doctor tries to kill the Dalek, Henry takes him out of 'the cage' and confines him, excited he's got another alien to add to his collection. While that's taking place, Rose is spending time with Adam Mitchell, one of van Statten's artefact collectors. He shows her the room where he reviews and catalogues all the alien artefacts he buys on the internet. They each discover they've got an interest in each other. Adam is happy when he learns Rose and the Doctor are just friends.
Using his ingeniousness, Adam breaks into one of the security cameras in the 'cage' to show Rose the Metaltron. When she sees it's being tortured she asks to go see it. When Rose walks in, she feels sorry for the creature and gently touches it. The Dalek is then able to absorb the residual temporal energies from her and regenerate itself. It breaks the chains confining it.
The chief in charge of torturing the Dalek rushes in, excited yet uncertain of what the Dalek can do. He sees the Dalek plunger arm and scoffs, "What are you gonna do, sucker me to death?" The Dalek then uses the plunger arm to sucker the man to death. Alarms are sounded and Henry van Statten is forced to halt his examination of the Doctor. The Doctor tells Henry to let him go if he wants to live. Reluctantly Henry agrees as the Dalek begins to go on a killing rampage, exterminating all that get in it's way.
When the Dalek comes face to face with Rose, it's unable to exterminate her. It has a sense of pity for her and later spares the life of Henry when Rose pleads with it. The Doctor realizes that when Rose touched it, the Dalek also absorbed some of her DNA. So with the regeneration, it began to develop feelings. Realizing it truly is a worthless Dalek, it destroys itself. van Statten's right-hand girl Diana Goddard has finally had enough of Henry and orders him to be removed with his memory wiped. The remaining security are all too happy to oblige.
MINOR COMPANION: Adam Mitchell
ORIGIN: Earth, circa 2012
REASON FOR JOINING: The Doctor is reluctant, but Rose asks for Adam to join the Tardis crew, knowing he has nowhere else to go. Hesitantly, the Doctor agrees.