De Haan was a part of Vishinsky's landing party, which discovered Sorenson and captured the Fourth Doctor. While on the probe ship, he discovered the body of Morelli and saw the beast that had attacked him, reporting this to Controller Salamar.
Unknown to him, this was the form Sorenson had been reduced to through contact with anti-matter minerals. While, De Haan was scanning the scene of Morelli's death for readings, he was attacked and killed by Sorenson, who left his dessicated corpse behind. (TV: Planet of Evil)