Morphant Master's possession of Bruce Gerhardt

Prior to his trial and execution on Skaro by the Daleks, the Master had planned ahead for this event, managing to survive via a Deathworm Morphant, having requested and been granted for the Doctor to have his remains returned to Gallifrey.

During this trip the Master's remains broke free, causing the Doctor's TARDIS to emergency land in San Francisco, 1999 where he would escape to subsequently possess the human body of Bruce Gerhardt. (TV:, PROSE: , etc.)