Synopsis
The Doctor (Jon Pertwee) and his assistants Jo Grant (Katy Manning) and Brigadier Lethbridge-Stewart (Nicholas Courtney) are investigating an unusual energy being that is intent to capture the Doctor as any cost.
Meanwhile, the Time Lords have detected a black hole to an antimatter universe, from which the energy being originated. They send the Doctors Second and First incarnations (Patrick Troughton and William Hartnell) to help his latest incarnation to escape the creature, and find out the origins of the black hole - the Time Lord pioneer Omega.