Original air dates 7 January – 28 January 1978.
Leela is flying the TARDIS through space. It stops. They find a new star system forming, and start getting sucked into it. They emergency jump to a nearby ship.
Ship was a race the time lords messed with. The people are hating the time lords. They have been on quest for a hundred thousand years. Trying to find a colony ship with a race bank that will let them restart their world. Crew is tired.
K9 flies the shape out of the star system, and fixes their ship. They find the colony ship, in the nebula. Doctor says they can’t go, is restrained, they go.
They fly through a meteor field and the gravity of the ship attracts all the meteors to them, entombing them in rock. They try and blast their way out, but it doesn’t work. Credits roll.
They break free to find a planet formed around their colony ship. They splash down onto the planet.
Inside the planet, chaos reigns as rocks fall from the sky. People run about in a panic. A masked person watches on a monitor, and arranges a troublemaker to be captured for sacrifice. Troublemaker is chanting heresy, treachery, encitement to escape. Masked men stop them.
Ship men break out of rock, monitored by the masked men. Inhabited world somehow. Ship men sneak out to find colony cylinders. Doctor and Leela follow them.
Masked men chase Doctor and Leela, running man runs out. Doctor and Leela hide, hear the plan to fumigate the tunnels, go back to the ship.
Ship men are in tunnels, too. Looking for colony ship. Lots of tunnels.
The Masked Men gas the tunnels. Gas fills the ship, as they left the doors open. Leela is sent with Escapee to the command deck to wait out the gas. Doctor goes out to stop gas something equally inscrutably Doctory. He finds the gas equipment and sonic screwdrivers it into reverse. Or tries to. Credits roll.
Gas us sucked back into the masked men’s area. They stop fumigation. Space crew finds the stolen stuff from their colony ship, want to liberate it. Doctor wants to save the captive and liberate all the slaves.
Doctor, Leela, and young slave find a grav-lift to the colony ship. It has elevator music.
There is a whole sacrifice ritual we sit through. Very moody and creepy. Doctor et al are caught, taken to Sacrifice. Young Slave interrupts sacrifice, big fight, big escape. Crew from ship rescues them. One stays behind to slow the advance, is captured.
Captured man is interrogated, the masked men revealing themselves to be “evolved from” the others, and have robot heads. Or something like it.
Doctor et al sneak in the crusher, and are dumped in the machine as credits roll.
Fight ensuses in tunnels. Space Crew fights off Guards. Doctor, Leela, Young Slave, and K9 head in a back way. Masked men realize they are losing and ask what the invaders want. They give them up, in exchange for the space man and the colony data.
Space Crew takes the colony data, prepares to leave.
Meanwhile, Doctor and crew sneak in the fumigation ducts to the colony ship. They get to the Oracle, and get the race bank thing as the Oracle calls for help.
Guards collapse the tunnel they’re in.
Space Crew prepares to leave. Doctor waits for rescue. K9 rescues them first. Finds that the Space Crew has bombs as decoys. Doctor runs into tunnels to dispose of them.
Doctor finds guards, who confiscate the cylinders and take the bombs back to the Oracle, who is also fooled. Oops.
Doctor takes slaves to Space Crew ship. Space Crew blasts out. Bombs go off, Space Crew surfs the explosion out. Doctor and Leela leave, with a reference to Jason.