A gangster hooks gangs of young women on drugs and has them commit robberies and prostitution.

The Master, an old adversary of the Doctor, has arrived on Earth to destroy humanity with the aid of the Nestene Consciousness and their army of Autons and killer plastic daffodils - unless the Doctor, joined by new assistant Jo Grant, can stop them.

Stodge City is in the grip of the Rumpo Kid and his gang. Mistaken identity again takes a hand as a 'sanitary engineer' named Marshal P. Knutt is mistaken for a law marshal. Being the conscientious sort, Marshal tries to help the town get rid of Rumpo, and a showdown is inevitable. Marshal has two aids—revenge-seeking Annie Oakley and his sanitary expertise.