The Master

The Doctor and his companion, Jo Grant, have been invited to Stangmoor Prison to observe a demonstration of a new device for treating hardened criminals, the Keller Machine - a device claimed to be capable of extracting negative emotions. The Doctor though is highly sceptical of the process. And this seems valid when a prisoner collapses during the demonstration whilst undergoing the treatment. The Doctor’s suspicions about the Keller Machine are heightened even further when it is revealed that there have been a string of deaths which all seem to occur when the Keller Machine is operated. Each death seems to be triggered by visions of personal phobias. Even The Doctor is affected when he gets too close to it. What The Doctor does not know, yet, is that the brains behind the Keller Machine, Emil Keller, is non other than The Master.

Meanwhile, The Brigadier is in charge of security at the first World Peace Conference. During which he is informed, by the Chinese delegation, that important documents have been stolen. But actually Captain Chin Lee, of the Chinese delegation, seems to be behaving strangely in an attempt to heighten tension in relations with the United States. Then the Chinese delegate dies in mysterious circumstances.

As well as looking after the security for the World Peace Conference, The Brigadier has delegated, to Captain Mike Yates, the responsibility to safely transport a banned nuclear powered missile with a warhead full of nerve gas, called the Thunderbolt, across the country so that it can be destroyed.

The Doctor

Back at the prison, while checking the Keller Machine, Professor Kettering, who is looking after the Keller Machine in the absence of Emil Keller, is killed when the machine suddenly becomes active. It is discovered, that he died due to drowning – something it seems Professor Kettering was terrified of. Realising that the Keller Machine is dangerous The Doctor insists that the machine must be destroyed but this is prevented by the Prisoner Governor who claims that he needs permission from the Home Office to do this.

The Doctor is then urgently summoned back to UNIT Headquarters, to assist The Brigadier with the unexplained death of the Chinese delegate. He leaves Jo Grant behind with orders that no one is to go near the machine. However, soon after leaving a riot breaks out and Jo is briefly taken hostage, but she is able to help the guards to retake the prison. But this return to order is short lived as The Master then arrives and helps the prisoners to retake control of the prison again.

The Doctor and The Brigadier

When The Doctor returns to the prison he is captured by The Master, who sets the Keller Machine loose on him, weakening The Doctor considerably. However, The Master is losing control of the Keller Machine, which contains a dangerous alien Mind Parasite, and so is forced to persuade The Doctor to help him contain its power.

What The Doctor and UNIT do not know is The Master has come to Stangmoor Prison to engage the prisoners as a private army which he then uses to hijack the UNIT convoy transporting the deadly Thunderbolt missile as it passes close to the prison. The missile is hijacked and Captain Mike Yates is captured after he follows the missile to an abandoned airfield. On learning of the loss of the missile The Brigadier tries to locate it by helicopter but fails. With the deadly missile now in The Master’s control he has it aimed at the Peace Conference – which he plans to disrupt and so cause a huge diplomatic incident.

Realising what The Master has done The Brigadier and UNIT troops re-take control of the prison, assuming that The Master must have taken the Thunderbolt missile there. But once the prison is under UNIT control it is discovered that the missile is not there. However, Captain Mike Yates, after he manages to escape from captivity, notifies The Brigadier that the Thunderbolt is being kept in an abandoned hangar at a nearby airfield. The Brigadier sets off to retrieve the missile but he soon discovers that The Master has disabled the abort mechanism on the missile so that when The Brigadier tries to destroy it nothing happens.

Jo Grant with Sergeant Benton

Back at the prison the Keller Machine is growing stronger and it soon breaks free of the temporary restraints placed on it by The Doctor. It now has sufficient power to move at random about attacking anyone it finds, leaving them dead. However, The Doctor and Jo discover that the presence of one of the prisoners, Barnham, inhibits the machine as he no longer has any evil for it to feed off.

The Master then contacts The Doctor. He wants a deal: his dematerialisation circuit, that The Doctor stole from his TARDIS, for the missile. With time running out The Doctor is forced to agree to meet him at the airfield. The Doctor though has realised that he can use the Keller machine against The Master. He uses Barnham as a shield so that he can transport the machine to the airfield. There he uses the machine to distract The Master so he can re-connect the missile’s abort mechanism. The Master though is able to escape from the machine’s attacks and drives off in the prison van. With The Master out of the way The Brigadier is able to blow up the missile, hopefully along with the Keller Machine.

Back at the prison, The Doctor is annoyed that The Master now has a fully working TARDIS again while he is still stuck on Earth. To make matters worse The Master phones The Doctor to taunt him with the promise that he will return to destroy the Earth one day.