Killer daffodils, a carnivorous armchair and the debut of The Master.
Remember the Nestene pod thingy that The Third Doctor left in UNIT’s care at the end of the epochal Spearhead from Space? Enter The Master, who promptly steals it. His ultimate goal is the subjugation of the human race by the Nestene Consciousness.
Before he summons an alien invasion force, however, he wants to incite chaos on Earth, not by releasing an army of killer Autons, but by having them don giant plastic heads and distribute killer plastic daffodils to an unsuspecting, locally contained public. Obviously, he also trials a few other murderous methods, such as a killer plastic demon doll, a killer phone cord and a killer inflatable armchair.
Pertwee, meanwhile, has a new companion in definitely-not-Doctor Jo Grant. Now the two of them, alongside Brigadier Alistair Gordon Lethbridge Stewart, new UNIT chap Yates and – perhaps to a lesser degree – the legendary Benton, try to fend off a Master-led Nestene invasion.