Although occasionally in the past Tommy Knight had reduced his involvement in the programme to concentrate on his school work, by 2009 Knight's studies had entered a more demanding phase. Nightmare accordingly wrote Luke Smith out as a series regular, but in such a way that occasional returns were narratively plausible. Similarly, Bob Baker had been less willing to allow the expanded use of K9 Mark IV that typified the previous two series, due to the 2010 transmission of his Australian K9 spin-off. Both Luke and K9 were therefore summarily bundled off to Oxford University at the end of this story, rarely to be heard from again. It was, however, an indulgent farewell for both characters, allowing them both significant parts to play in the action.