The Doctor and Jo discover The Master and the Ogrons are the masterminds behind the Galactic war between the Earth Federation and the Reptillian Draconian Empire and the Master has framed The Doctor and Jo as spies working for the Draconians. Only to discover The Master is also working with the Doctor's greatest enemies, The Daleks, who are also behind the galactic war.

The Doctor is sentenced to life imprisonment at a lunar penal colony while Jo encounters an old enemy.