A New Face
Unstable from his recent regeneration, The Doctor is confined to sick bay. The Brigadier though is desperate for The Doctor to recover so that the Time Lord can assist UNIT in the investigation into the theft of top secret plans and equipment from supposedly secure premises.
The thefts of electronic components and secret plans have been happening both at night and in broad daylight and when The Doctor finally recovers, he inspects the site of the most recent theft and realises that they are up against something distinctly non-human as heavy vehicle tracks have been found in the vicinity of the supposedly secure buildings which housed the components. In a later incident, the perpetrator actually drills through the ground to gain access to a heavily armed vault to steal a valuable piece of electronics.
Meanwhile, Sarah Jane Smith decides to use the opportunity to investigate a top secret government Think-Tank, a body involved in developing emerging technologies, and inadvertently discovers that the raids have been carried out by a robot invented by scientist Professor Kettlewell who has been working for Think-Tank.
|The Doctor with Harry Sullivan
However, when Sarah first arrives at Think-Tank and is escorted around, by Miss Winters the director of Think-Tank. Sarah though discovers nothing untoward – except for a suspicious of a patch of oil on the floor of Professor Kettlewell's deserted lab. After sneaking back there to investigate further she comes face-to-face with the silver robot when it suddenly appears from behind a hidden door and strides starts to stride her demanding to know who she is and why she is there.
As Sarah starts to panic and backs away as the robot advances Miss Winters arrives and tries to convince Sarah that the robot is incapable of harming anyone or doing anything that will harm the human race due to an inhibitor.
|A New Costume
However, it transpires that the robot has been re-programmed, on the orders of Miss Winters, and used to obtain plans and equipment for the construction of a disintegrator gun with which the Scientific Reform Society - of which she is a leading member - can obtain the computer codes controlling the nuclear weapons of the world's leading powers. In this way, the Scientific Reform Society intends to hold the world to ransom unless their demands for a purer way of life are met.
Professor Kettlewell, although claiming no knowledge of Miss Winters's activities, is actually a party to them. Realising that The Doctor is a danger to their plans Professor Kettlewell tricks The Doctor in meeting him in his lab. However, when The Doctor gets there, he is confronted by the robot that has instructions to kill him. At first The Doctor is unable to escape from the advancing robot due to its size and its determination to carry out its instructions. The Doctor though manages to escape when some UNIT troops arrive.
Professor Kettlewell, on witnessing that his creation is being abused in this way, realises the error he has made. But when he balks at Miss Winters' ruthlessness he is accidentally killed by his creation when he tries to stop the robot from wiping out the group of UNIT troops.
|Sarah and The Doctor
Upon killing its creator the robot suffers an electronic/mental breakdown and tries to activate the nuclear weapons. Sarah, realising the turmoil the robot is in, tries to reason with it but instead finds herself kidnapped.
The Brigadier attempts to destroy the robot with the disintegrator gun, but this merely causes it to grow to gigantic proportions, following which it goes on the rampage through the UNIT troops, protecting only Sarah with whom it feels an affinity.
The Doctor, assisted by UNIT’s medical officer Surgeon Lieutenant Harry Sullivan, manages to save the day, and also rescue Sarah, by brewing up a virulent metal virus described in Kettlewell's notes and using it to eat away the giant robot until there is nothing left but a small heap of decaying rust, which itself is soon destroyed by the virus.
With the problem sorted out, The Doctor, now fully recovered following his regeneration, decides that the time has come to travel once more. He persuades Sarah and Harry to join him and so they all enter the TARDIS. The Brigadier though is less than pleased to see the TARDIS dematerialise, as The Doctor has been invited to an audience at Buckingham Palace.