'This sounds like you have OCD.' Dr Patel looked at the gangly teenager, and spoke in a sympathetic tone. 'How long have you had these thoughts?'

'Since as long as I can remember,' the boy said. 'I have to get some sort of help. I'm so disgusting.'

'Not at all,' Dr Patel said. 'We can get you an appointment in three weeks for some CBT.'

'That would be good.' The teenager's face was a picture of relief. His demeanour changed as he left Dr Patel's office. Finally he had a diagnosis, and some reassurance for the horrible intrusive thoughts plaguing his mind. Thoughts he couldn't tell anyone about. Dr Patel had done more for him in those few minutes than any other doctor.

He walked down the stairs, his obsession with possibly having killed someone robbed of its power, but the awful doubts still persisted. What if he had lied to Dr Patel? What if he didn't have OCD after all?

His phone rang.

'How was it?' came the voice on the other end. 'What did they say?'

'All right,' he said. 'I'm having some therapy. It's not like Kyrex B at all. These Earth psychiatrists really know their stuff.'