Inner Demons was meant to show what Chrístõ might be like if he was not a nice person, the antithesis of himself. I wanted to show him acting moodily, selfishly, downright nastily towards his friends, before eventually doing something absolutely terrifying. His sudden attack on Bo, accusing him of playing with his affections only to leave him for Sammie was completely irrational, of course, since he had quite gently pushed her towards him. Even more insane was his reaction to Cassie, telling her that her baby was a demon that had to be cut out of the womb. This wasn’t completely original. I saw something similar in an X-Files graphic novel in which a gynecologist went off the deep end believing that aliens were out to get him.

The realisation that something was fundamentally wrong with Chrístõ was a shock to his friends. When they found out exactly WHAT was wrong with him it was even more so.

There is no particular inspiration for the creature found to be growing inside him. The go'ould in Stargate are vaguely the same idea, but I wasn’t really going by them. The Werewolf Host as described in Tooth and Claw is a little bit in the same vein, too. But this is a different entity entirely and Chrístõ is at its mercy unless his friends can take the most desperate measures of all.

There is an irony, of course, in that Sammie performs this operation on Chrístõ when, not so long before, he operated to save Sammie’s life. The operation itself is routine except for the fact that Time Lords don’t tolerate anaesthetic and he goes through it all using his meditative trance just as The Doctor does in a couple of stories in the Unfinished Business and New Lords of Time series.

The creature is destroyed and Chrístõ is well. The last paragraph, where he said they would go for a holiday in Ireland confused a lot of people who expected a story based in Ireland to be next. It really was just a throwaway joke to round off the story.