Parts: 3
Writer: Louis Marks
Airdates: 31 October 1964 - 14 November 1964
Production Code: J

Episode Titles: Planet of Giants; Dangerous Journey; Crisis

Doctor: first
Companions: Susan, Ian, Barbara

Story: Yet another attempt by the Doctor to get Ian and Barbara back to their proper time results in a number of malfunctions, including the TARDIS doors opening while in flight. Ian, Barbara and Susan manage to force them closed again, and then the TARDIS materializes. While they explore, the Doctor and Barbara find an enormous dead snake; Ian and Susan come across an enormous dead ant. Realizing that the enormous dead snake is actually an enormous dead earthworm, the Doctor begins to suspect that somehow the TARDIS and its occupants have shrunk. In fact, this is exactly what has happened; the pressure when the doors opened caused the TARDIS to miniaturize, and they have landed between stones in the paving of a garden.

Ian and Susan have found a large matchbox, and when they are startled by a shadow and loud noise, Ian hides within it. Both shadow and noise were produced by a man, Farrow, who picks up the matchbox. A second man, Forester, arrives - he is manufacturing an insecticide called DN6, and Farrow has come to evaluate it for the government. When Farrow informs Forester that he cannot approve it, Forester shoots him.

It's up to the Doctor and his companions to stop Forester from unleashing his deadly insecticide upon the world - but being only one inch tall, the travellers will have to rely upon the Doctor's ingenuity to surmount their monumental task. And when Barbara is poisoned from touching a seed infected with DN6, the stakes are suddenly raised higher...