Former Coronation Street star Michelle Holmes stars in Casualty (Sat, April 2, BBC1) as a mouthy mother – but does she know best?

This week you play the mother of Sally, who is admitted to the psychiatric ward after attacking a fellow university student. How does your character, Donna, react to her daughter’s illness?
“Donna doesn’t take any prisoners. When it comes to finding out what’s wrong with her daughter she’s quite strong willed with the staff – especially at first when she doesn’t believe Sally is ill!”

Why doesn’t Donna believe Sally might be suffering from a mental illness resulting in paranoia?
“Because Sally’s home had two break-ins, her laptop has been stolen and things have gone missing at University. Donna believes it adds up to conspiracy. Sally’s doing important research work that is attracting attention from big corporations so, in a way, it all seemed to add up.”

When does she finally accept her daughter is ill?
“She’s finally convinced her daughter is ill when she sees the evidence of her paranoia and symptoms of madness for herself.”

But there’s a twist to the story?
“Ruth, who is also in the mental health unit, diagnoses Sally with Lyme disease. Apparently Lyme Disease makes you seem completely mad as, if you get bitten, you show symptoms of paranoia and madness.”

Is Sally OK by the end?
“Yes! They give her a course of antibiotics and that clears it up. Apparently, it’s quite common.”

Will you watch the episode when it screens?
“This is a great story and really interesting. But I’m not sure if I can watch it. I’m a total hypochondriac and quite squeamish so I find it hard to watch any medical dramas. No matter how fantastic they are I’m bound to think I’m ill the week after!”