The Sontaran Experiment

Synopsis

The Doctor, Sarah and Harry arrive on a desolate and apparently deserted Earth to discover that a group of shipwrecked astronauts from a human colony, GalSec, have been lured there by a fake distress call. One of their number, Roth, tells Sarah of an alien conducting gruesome experiments on him and his crewmates. The alien turns out to be a Sontaran, Field-Major Styre, who is compiling a report on human physical and mental capabilities as a prelude to an invasion of Earth.

The Doctor challenges Styre to unarmed combat. The Sontaran agrees but is quickly weakened in Earth's unfamiliar gravity. Harry meanwhile enters Styre's ship and uses the Doctor's sonic screwdriver to remove the vital terullian diode bypass transformer, so that when the alien returns there to revitalise himself he is drained of all his energy and destroyed.

The Doctor sends a message to the Sontaran fleet, warning them that without Styre's report they cannot invade.

Cast
The Doctor - Tom Baker
Sarah Jane Smith - Elisabeth Sladen
Harry Sullivan - Ian Marter
Vural - Donald Douglas
Krans - Glyn Jones
Erak - Peter Walshe
Styre / The Marshal - Kevin Lindsay
Roth - Peter Rutherford
Zake - Terry Walsh
Prisoner - Brian Ellis