The Masters plan is to steal a nerve gas filled nuclear power missile called Thunderbolt with the help of the escaped prisoners-in order to destroyed the peace conference and start a nuclear war after which he can become overlord of the planet. The Keller machine,becoming more intelligent the more negative energy it absorbs, is now free floating about Stagmoor-injuring and killing everyone in sight. Mailer does while attempting to kill the doctor,shortly after which the doctor realizes that due to a shield created by Barnhams mind,rendered servile and childlike by the machine,disables it from killing. While the doctor,Jo and Barnham waits with the machine, the Brigadier and Benton prepare to infiltrate Stagmoor to disable the Thunderbolts activation device-using the time circuit removed by the doctor as a bargaining chip. The Master agrees for the doctor to go there alone, Jo and Barnham follow. The doctor loses the Masters time circuit back to him in the ensuing scuffle,Barnham is knocked unconscious before the Thunderbolt is detonated at the hanger-after which Jo morns the death of Barnham and the doctor laments his exile on Earth in lieu of the now freed master.
Though The Master's intention in this story is almost childishly simple in his terms,his credo of living for the challenge is played up here as his plans for achieving his goal is extraordinarily complicated. The doctors immediate dislike for the intention behind the Keller process,soon found to be just as insidious as the doctor predicted,is also realized by the Masters intent to masquerade his plan for world domination clothed in the good deeds of criminal reform. In keeping with the sociopolitical orientation of the first two third doctor series' of the program, this episode tackles the issue of Communism in the place of Red China. Chin Lee is very easily manipulated into high level espionage by the Master due to her beguiling manner. One wonderful scene is the respect delegation leader Fu Peng has for the doctor when he honors him with his native Hokkien dialect and the traditional bowing-where the Brigadiers adherence only to Western traditions such as hand shakes and the English language are seen as hostile. Again the Brigadier,while benevolent in intention,is shown to have much to learn from the doctor. Jo,while often scared is often wily enough to escape tight spots on her own at this early juncture. And even The Master,while equal in ability and intelligence,seems to have much to learn from the doctor as well.