A malfunction of the TARDIS systems reduces the Doctor and his companions to just an inch in height. In their miniaturised state, they arrive in contemporary England and stumble across a plot by a ruthless businessman, Forester (Alan Tilvern), and his misguided scientist colleague, Smithers (Reginald Barratt), to launch a new insecticide, DN6 - a product so destructive that it would kill not only those insects harmful to agriculture but also those vital to it. Forester is even willing to commit murder to ensure the success of his business, as civil servant Arnold Farrow (Frank Crawshaw) discovers to his cost.

The criminals are eventually brought to justice when the Doctor and his friends - hampered by the fact that Barbara has herself been made ill by the insecticide - tamper with the telephone in Smithers's laboratory, thus fuelling the suspicions of the local exchange operator, Hilda Rowse (Rosemary Johnson), who sends her police constable husband, Bert (Fred Ferris), to investigate.

Synopsis from Doctor Who: The First Doctor Handbook by David J. Howe, Mark Stammers and Stephen James Walker, reprinted with permission; further reproduction is not permitted. Available from Telos