PentoCyleinicMethyldrane

PentoCyleinicMethyldrane (or PCM) was a drug used by the Company to alter the emotions and will power of its subjects. Around Megropolis One, there were eight vapour towers in which the PCM was stored with each one controlled from a central point at Main Control. PCM had a critical temperature of 205 centigrade, maintained at this central control. Prior to his arrest, Bisham's job was in the manufacture of PCM.

PCM was extremely important to the Company as it kept the subjects in order and submissive of their harsh treatment. Bisham noted that:

"The PCM is the source of the Company's power"

- Bisham

For this reason, the Fourth Doctor chose the PCM control as the target of his rebellion. The rebel leader, Mandrel, had previously worked at Main Control so he knew how to operate the system.

The rebels attacked Main Control and forced the two guards there to surrender. Mandrel then closed fown the vapour towers and maintained the PCM temperature at 70 centigrade. With this, the PCM in the atmosphere fell dramatically to three parts in a thousand. (DW: The Sun Makers)