Stien encountered the Fifth Doctor and Tegan Jovanka after they landed in London 1984 due to falling into a time corridor. Stien escaped from the Daleks as he could not take the Dalek conditioning. He next travelled with the Doctor through the time corridor to a prison ship the Daleks had boarded.
However, the conditioning re-emerged and he threatened the Doctor and took him as a prisoner. He began processing the Doctor for the same Dalek conditioning when he began having second thoughts. With the Doctor's assistance, Stien was able to regain control of his mind.