The Tardis has materialized inside a space craft in the year 2540. Currently, Earth and the Draconian empire are on the verge of war. The Doctor and Jo are accused of being Draconian spies. Things get confusing when the Earth men actually start to see Jo and the Doctor as Draconians. It turns out, some outside force is making the crew of the ship see what they fear most, apparently Draconians.
But the problem isn't limited to this ship alone. Both Draconian and Earth ships alike believe they are being attacked by each other. The Doctor sees through this illusion and realizes it's actually the Ogrons using a hypnosis device to trick Earth and Draconia into a war, neither truly wants. But the Ogrons are sort of intergalactic thugs out for hire. This isn't something they'd do on their own.
The Doctor and Jo are sent to Earth and separated, but are reunited by the true Master-mind of the devious plot. The Master has once again escaped incarceration and vows to see Earth and the Doctor destroyed. However the Doctor has influence in the Draconian empire and convinces the Emperor of the Master's plot.
As shown time and time again, the Master is not so easy to capture. Using his hypno-device which makes people see things they fear he escapes, though Jo fights through the illusion much to the dismay of the Master. Unfortunately, this is the last time Roger Delgado plays the Master. Several months after filming, the actor dies in a car accident. Instead of recasting someone new to play the Master, this is his last appearance in Doctor Who for several years.
As the Master makes his escape, he shoots the Doctor. Things look grim, but Jo helps the Doctor into the Tardis where he begin his recuperation. He also contacts the Timelords after finding out the Master was working with the Daleks all along. They have now begun to resurface and are bent on global domination once more. The Timelords direct the Tardis to the Daleks base of operation. This leads directly into the next story (not being reviewed by me next week).
WHO: The Master
DEPARTURE LOCATION: Ogron Homeworld - 2540
REASON FOR DEPARTURE: Never a part of the Tardis crew.
Next: It's Not Easy Being Green