After making some alarming discoveries, neurosurgeon Roxanna MacMillan confronts Professor John Gaskell in next week's Holby City. And her actions have dramatic consequences as Hermione Gulliford reveals...

Roxanna’s meddling into Gaskell’s trial has tragic consequences, as Holby City star Hermione Gulliford reveals…

How did neurosurgeon Roxanna MacMillan go from wanting to be part of Professor John Gaskell’s pioneering stem cell trial to stepping down from it, then ‘investigating’ her friend?

Hermione Gulliford: “Roxanna always wanted to be part of Gaskell’s trial because she admires the radical way he’s trying to change modern medicine. But she now fears his ambition to find a cure for degenerative diseases is at the expense of the patients involved. I don’t think Roxanna believes Gaskell’s doing anything purposefully manipulative. It’s just that he’s become all-consumed by this trial and she needs to find out the truth about what’s going on.”

Holby Roxanna digs for dirt on Gaskell

Roxanna fears Gaskell is taking risks and makes it her mission to find out what he’s up to

Convinced Gaskell (Paul McGann) is hiding something, Roxanna wants to get into his wet lab to hunt for information. Can anyone help her gain access?

HG: “Yes, young doctor Meena Chowdhury (Salma Hoque) has been involved with the trial on and off, so Roxanna asks her for help. Meena’s experienced Gaskell on a bad day and doesn’t want to put her career in any more jeopardy but, at the same time, she believes Roxanna’s trying to do the right thing. So Meena gives Roxanna the entry code – albeit secretly – so she can get into the wet lab and find out what Gaskell’s been up to.”

What does Roxanna find once she’s in there? And is there a chance she’ll get caught?

HG: “Roxanna discovers Gaskell hasn’t got rid of patient Julie Bloom’s embryonic stem cells, like he said he would, as ‘ethically’ they couldn’t be used. There’s definitely a chance Roxanna might get caught in the wet lab. In fact, it turns out Gaskell’s actually on his way down, so Roxanna has to make a quick getaway. Then, back on the ward, Roxanna makes a huge discovery about Laszlo Furz, the man Gaskell cured of motor-neurone disease…”

Holby Roxanna and Laszlo Furz

Behind Gaskell’s back, Roxanna calls Laszlo Furz into the hospital and makes a shock discovery

Having made all these discoveries, does Roxanna confront Gaskell with what she knows?

HG: “Yes! Roxanna and Gaskell are old friends, so she doesn’t want to ‘blow the whistle’ on him; she hopes they can work things out together. So Roxanna meets Gaskell in Albie’s bar, where she’s certain she’ll be able to have a reasonable conversation with him and that he’ll listen to her when she reveals her findings and urges him to stop the trail. However, Roxanna soon realises she’s not going to get through to Gaskell – that’s when she tells him she’s going to talk to Hanssen!”

Gaskell’s not happy when Roxanna confronts him over what she’s discovered

We can’t imagine Gaskell likes that! What happens then?

HG: “Gaskell chases after Roxanna and, as they argue, he threatens her. Outside, their argument gets very physical and I think, for the first time ever, Roxanna’s genuinely scared of him. She hasn’t seen this dark side of Gaskell before and she does everything she can to get away from him. But no one could have predicted what happens next…”

Watch the story unfold on Holby City, Tuesday September 11 at 8pm on BBC1.