In the London Underground people have been going missing since the 19th century. While the Doctor and Majenta Pryce go to see the play The Mousetrap, they find the Underground filled with ghosts from different Earth eras.
A man is sweeping up a train when a ghostly girl suddenly appears in front of him. He gets the shock of his life when hundreds of ghosts fly in and advance towards him.
The next day the Doctor and Majenta Pryce are on a train in the London Underground to their way to see The Mousetrap when the train stops. The Doctor's sonic screwdriver picks up a psychic pulse from somewhere down a tunnel. They leave the train, leaving some of the passengers worried by the Doctor's talk of "aliens".
As they walk down the tunnel, they find the cleaner who had been taken by the ghosts. He is now a ghost himself. He attacks the Doctor. Majenta picks up the screwdriver and zaps the man. He turns back to his normal self but is still a ghost. His name is Eddie Lang. the Doctor tries to tell him he is dead, but Majenta just blurts it out. He starts ranting on about a machine and then runs off.
On the Northern Line a train starts speeding down, when suddenly the same ghostly girl appears. The train stops just in time; the driver speaks on his phone but he is cut off.
While searching for the man, the Doctor tells Majenta that there is no such thing as ghosts. He says they are time leaks and psychic imprints. The Doctor opens a gate and they find "ghosts" of all eras. They ignore them and continue following the psychic pulse. The Doctor says it is just him and Majenta in the tunnels. Then a voice booms, "And me".
The passengers on the stopped train talk to the girl, who says "Look, look up." Ghostly figures advance on them and she starts to laugh.
The Doctor and Majenta find a cybernetic woman in the tunnels who knows their names. She has read their minds. Her name is Mnemosyne and she says all the people, including the Doctor and Majenta, are part of her now. The ghosts begin advancing on them.
Twenty minutes before the previous event, the staff at underground control are miffed at the trains stopping. An employee says to his boss, Brian, that he is not sure why.
Two minutes later Mnemosyne has the "ghosts" restrain the Doctor and Majenta. Mnemosyne tells the story of how she got to planet Earth, a hundred and seven years ago.
Her master, an alien, stole a Mnemosyne unit and sold the technology across the galaxy. He was successful until he came to Earth where the humans battered him to death. Mnemosyne hid in the London Underground, recording psychic patterns of her master.
She proceeds to the next step in her plan. She takes over television screens and broadcasts her message, saying she will destroy Earth. Majenta does not understand why, but the Doctor says it is because Mnemosyne wants revenge; she is programmed to mourn the dead, and she fell in love with her master. The Doctor runs off to stall them, asking Majenta to negotiate with them.
The Doctor looks for the junction box and finds a train. He sees that everyone there has been turned into ghosts. He finds the ghostly girl, who turns out to be Mnemosyne in another form. The Doctor refuses to give himself up and runs, only to have the ghosts chase him.
Majenta negotiates with Mnemsyne. The "ghosts" tell her to shut up, but the "ghost" of Eddie tells them to hear her out. The "ghosts" say that they are fed up with being lonely. Eddie agrees to help Majenta if she will care for them when they are gone and she promises to do so.
The Doctor finds the junction box, but the girl finds him and he is grabbed by the ghosts. They hold him, ready for him to get hit by a train.
Eddie confronts Mnemosyne, but she says he should obey her. He hits her on the head with his brush and the "ghosts" attack her. She falls to the floor and begs Majenta to save her, but Majenta smashes Mnemosyne's head and the "ghosts" begin to fade away.
The Doctor yanks the cables out just in time and the train does not hit him. Meanwhile at Underground control, Brian says that UNIT clearance will clear away the mess. He says on f the phone that the crisis is over. The girl, who has not faded away, says:
"Is it Doctor? Just remember what I said. When the time comes I'll be waiting... ... We'll all be waiting"
As the Doctor and Majenta leaves, Majenta suggests they go and see The Mousetrap. The Doctor says no, he is going to Panacea right now. He tells her it is over. A voice comes from the sky, saying it is the voice of Justice, and Intersol has this world completely surrounded. They demand that she come out with her hands up.
- The ending of this comic leads directly into the comic story The Crimson Hand.
- The events of the "War of Medusa Cascade" are mentioned. (TV: The Stolen Earth / Journey's End)
- The Doctor says he doesn't take companions anymore, and that Majenta's journey with him is merely a job. (TV: Planet of the Dead)
- The ghostly girls warn the Doctor about his approaching demise. (TV: The End of Time)
- The Doctor once again promises that he will take Majenta to Panacea. (COMIC: The Stockbridge Child etc)