Elisabeth Sladen – Sarah Jane Smith
Daniel Anthony – Clyde Langer
Anjli Mohindra – Rani Chandra
Alexander Armstrong – Mr Smith
Tommy Knight – Luke Smith
Matt Smith – The Doctor
Katy Manning – Jo Jones
Finn Jones – Santiago Jones
Laila Rouass – Colonel Karim
Ace Bhatti – Haresh Chandra
Jimmy Vee – Groske
Phillip Hurd-Wood – Groske voice
David Bradley – Shansheeth voice
Jon Glover – Additional Shansheeth voices
Paul Kasey – Shansheeth
Rauri Mears – Shansheeth
Ben Ashley – Shansheeth
Directed by Ashley Way
Written by Russell T Davies
Script editor Gary Russell
Produced by Brian Minchin
Phil Ford (co-producer)
Executive producer(s) Russell T Davies
Production code 4.5 and 4.6
Series Series 4
Length 2 episodes, 25 minutes each
Originally broadcast 25 & 26 October 2010
UNIT forces, led by Colonel Karim, converge on Sarah Jane's home, and inform her, Rani, and Clyde that the Doctor is dead. Karim explains that members of the vulture-like race, the Shansheeth, found the Doctor's body and have brought it to Earth for a proper ceremony, to be held at the secured UNIT Base 5 underneath Snowdon. Sarah Jane is skeptical, knowing of the Doctor's ability to regenerate, but agrees to go along with Rani and Clyde.
At UNIT Base 5, the three are initially surprised to see what appear to be Graske aliens, a species they had difficulties with before, but learn that they are really Groske, a cousin species to the Graske and working peacefully to maintain the base. Karim explains that after the ceremony they plan to launch the Doctor's body into space using a rocket built by the Groske. As they tour the now-sealed facility, Clyde feels energy coursing through his hand, recognising it as the same artron energy he felt when he accidentally touched the dematerialising TARDIS during the events of The Wedding of Sarah Jane Smith. The group later meets another of the Doctor's former companions, Jo Grant, now married and going by Jo Jones, along with her grandson Santiago. Sarah Jane and Jo discuss the possibility of the Doctor's death, and agree that this may be a trap set up by one of the Doctor's enemies, while Rani and Clyde make quick friends with Santiago.
Rani, Clyde, and Santiago are met by the lead Groske, who tells them there is an increase in artron energy in the area and leads them through an air vent to where the Shansheeth have stored the Doctor's body as well as the TARDIS. They overhear the Shansheeth's plot to capture Sarah Jane and Jo and use a Memory Weave to drain their minds, before the Shansheeth discover their presence. The group locate Sarah Jane and Jo and warn them, just as Clyde feels more surges of artron energy. Suddenly, Clyde's body is replaced with that of the Doctor in his latest incarnation, the Eleventh Doctor. Once Sarah Jane and Jo recognise the stranger as the Doctor, he explains he used the artron energy to swap places with Clyde from a world 10,000 light years distant. The Shansheeth catch up to the group and fire a beam of energy at the Doctor—assuring that they will have the death of the Doctor, after all.
As he is struck by the energy, the Doctor's body is replaced with Clyde's, temporarily confusing the aliens and allowing the group to find safety. The Doctor swaps places with Clyde again, then holds onto Sarah Jane and Jo before performing another swap, taking all three back to the alien world. With their help, the Doctor is able to repair the device that he has been using to perform these exchanges, allowing them to return to Earth without displacing Clyde's body.
Meanwhile, the children and lead Groske determine that for the Shansheeth plan to have worked, they needed help from someone in UNIT. Using the air vents, they learn that Karim is working with the Shansheeth. Their plan is to recreate the TARDIS key from Sarah Jane's and Jo's memories, such that the Shansheeth can use the time machine to stop death across the universe by interfering with timelines and Karim can leave Earth as there is nothing left for her here. Karim discovers the group's presence in the air vents and heats them up. The Doctor, Sarah Jane, and Jo return to Earth, but as they go to rescue the children, Sarah Jane and Jo are captured and secured in place. The Doctor safely rescues the children and the Groske. They find the room where Karim and Shansheeth are preparing to use the Memory Weave on the Doctor's former companions, but are unable to open the sealed door with the Doctor's sonic screwdriver.
As the Weave starts to pull the memories of the TARDIS key from Sarah Jane and Jo, the Doctor gets the idea to overload the machine. He shouts through the door for Sarah Jane and Jo to recall all their memories of their time with him, and encourages the children to do the same. The Weave is overwhelmed and begins to self-destruct, which will kill everyone in the room. Sarah Jane and Jo free themselves and, realising that the coffin brought by the Shansheeth can protect them from the blast, close themselves inside. Karim and the Shansheeth are killed in the explosion, which blows the door off. The Doctor and the children are relieved to find Sarah Jane and Jo safe.
After assuring the threat is over, the Doctor uses the TARDIS to return the group back to Sarah Jane's home and says his goodbyes before leaving. Jo and Santiago say their goodbyes and depart as well. Rani and Clyde inquire about the Doctor's other companions, whom Sarah Jane has researched and learned many have gone on to do great things for the human race. She reflects that with their legacy and memories, the Doctor will surely never die.