Casualty‘s Tristan Gemmill talks about his character Adam discovering his latest patient is a sex offender in this Saturday’s episode on BBC One…

Adam has to treat a known sex offender this week – can you tell us what happens?
“Adam’s been feeling frustrated with the medical system for a few weeks now. At first he treats the sex offender Matthew for his injuries like he would any other patient. But when Matthew makes a cry for help, claiming he can’t stop himself, Adam realises he’s going to have to step in. Otherwise Matthew could go on to attack another young girl.”

Can you reveal what happens next?
“Adam decides to take matters into his own hands and pays a visit to the hospital pharmacist. I won’t give away the ending, but it’s the start of a downhill spiral for Adam. He begins to develop a bit of a God complex and breaks all the rules.”

It sounds like a heavy storyline, did you find any way of breaking the tension on set?
“Fortunately I had guest star Denise Welch, who played Matthew’s mum, to lighten the mood between takes. I’d known her for about 15 minutes and we were already giggling – the woman is an absolute hoot!”

Did you enjoy working with Gavin Bell who played Matthew?
“He was fantastic. He captured an eerie humanity which stopped you from thinking he was just a monster. He managed to somehow make you feel sorry for his character. In real life Gavin’s in a great band called Amber State – he acts to support his music. He’s a very talented guy.”

You’ve got two young children, did that make the episode harder to film?
“A little – but I think there’s a bit of paranoia as well about the paedophile situation. I would obviously never put my children in danger, and I know there are some disturbed people out there, but it would be sad if they never spoke to people they didn’t know.”

Do you have any other good storylines coming up?
“I can’t give too much away, but I can say that Adam’s current behaviour will certainly catch up with him. It all turns into chaos at the end of this series!”