Marc Cory (Edward de Souza), an agent of the Space Security Service, has been despatched on a secret mission to the planet Kembel to investigate a recent sighting of a Dalek spaceship. Cory's suspicion that the creatures may have established a base on Kembel proves well-founded. His two companions, Jeff Garvey (Barry Jackson) and Gordon Lowery (Jeremy Young), both fall victim to the poisonous thorns of Varga plants (Tony Starn, Roy Reeves, Leslie Weeks) - flora indigenous to the Daleks' home world, Skaro - and he has no choice but to shoot them before they are themselves transformed into Vargas.

Having overheard the Daleks (Robert Jewell, Kevin Manser, John Scott Martin, Gerald Taylor; voiced by Peter Hawkins, David Graham) plotting with Malpha (Robert Cartland), Trantis (Ronald Rich) and other alien allies (Johnny Clayton, Pat Gorman, Sam Mansaray, Len Russell) to invade Earth's galaxy, Cory records a warning message and prepares to send it into orbit with a rocket launcher. Before he can do so he is discovered and exterminated, but the Daleks fail to destroy the tape, so the information that he has gathered still exists to be discovered.

_{Synopsis from Doctor Who: The First Doctor Handbook by David J. Howe, Mark Stammers and Stephen James Walker, reprinted with permission; further reproduction is not permitted. Available from Telos}