Pietersen was a colonist that lived on an asteroid of gold, spending most of his time playing chess with Badenhorst while they awaited word from Kellman to clarify if it was safe for them to journey to the Nerva Beacon to join their vanguard, Joseph. However, upon the arrival of the Fourth Doctor, it was exposed that Kellman had killed Joseph to keep the asteroid a secret from the Nerva so he could steal the gold for himself, and Pietersen was shot and killed as Kellman made his escape. (AUDIO: Return of the Cybermen)