'This story is told as a series of reports and interviews. It is an investigation into a company called Planetary Conversions which specializes in 'bloodless' invasions. The investigation is carried out on behalf of the Department of Auditing and Accountability. It is chiefly concerned with a project run by Planetary Conversions on behalf of the Doctor on Trycos 3; the planet has descended into a state of barbarism which threatens to wipe out more than two billion inhabitants. The Doctor offered up mining rights in the northern hemisphere for a valuable mineral called Jethryk in return for the deployment of a pacifying drug that would make the inhabitants susceptible to re-education by teams of automatons. When the directors of Planetary Conversions realised that the best deposits of Jethryk were on the rest of the planet they decided to portray the Doctor as a terrorist and have him assassinated. This would nullify the contract and allow the company to assume control of the planet for themselves. The Doctor survived the assassination attempt and put his own retaliation in place: extracting a coded password from the subconscious mind of a low level employee and gassing the board of directors with their own pacification drug, thus causing them to confess their own activities and effectively putting themselves out of business.'
[The Doctor is the Seventh Doctor.]
Source: drwhoguide.com (http://www.drwhoguide.com/whotrip28.htm). Sighted 20/5/11