“It won’t end well!”

Casualty spoilers follow.

Note – This article contains discussion of sexual abuse.

Casualty‘s Siobhan McKenzie was introduced earlier this year as Holby’s new clinical nurse manager. But in the current series, ‘Storm Damage’, viewers were surprised to see her promoted to clinical lead – replacing Patrick Onley, who left in disgrace.

In an exclusive chat, actor Melanie Hill describes her character’s new role as a “gift” to play, but for Siobhan, she has had to prove herself in a job that doctors primarily occupy.

“She struggles to be taken seriously,” she said, “as it is only a temporary position. And she has to do her own job on top of everything else and be a line manager for the nurses.”

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Siobhan has been front and centre in the current run of the medical drama, steering her team through challenges when a storm ripped through Holby, creating chaos in the ED.

But as well as this, viewers have learned more about Siobhan’s personal life in this series – through a big twist that no one saw coming.

In the opening episode, Stevie worked a shift with the helicopter emergency medical services (HEMS), where she was called to a challenging incident and met Rich, a firefighter who was in charge of the response.

The pair quickly formed a connection as they worked together, and afterwards Rich gave Stevie his number. But it was then that she spotted the ring on his finger and realised he was married, so she backed off.

They continued to text though, and while Stevie was unsure about the morals of what she was doing, she was encouraged by colleague Siobhan to have a bit of fun and meet up with him.

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But soon after, viewers met Siobhan’s husband for the first time, and found out the shocking revelation that she is married to Rich, the very man that Stevie was becoming entangled with.

“Siobhan was eased in gradually [to the show]”, Melanie explained, “which is a good way to join Casualty. But the more you learn about your character, the better you’re able to play them.

“And the scene in the rain when Siobhan got into the car and you discovered that Rich was her husband… I had people messaging me who were just like, ‘oh my god!'”

Stevie and Rich began a proper affair, but it was only later that she realised she was seeing Siobhan’s husband behind her back. Her guilt then took over, but Rich wanted to prove he was serious about her and decided to end his 25-year marriage to Siobhan.

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It is a bombshell that blindsided the clinical lead, but she suspects that there is another woman involved – a suspicion that she shares with Stevie, no less. Melanie confirms that an upcoming scene will see Siobhan find a receipt for cocktails that makes her investigate further.

But despite all this, Siobhan doesn’t want to give up, and Melanie says that her character will “do anything to make her marriage work”.

While Stevie and Rich’s liaison remains under wraps for now, it seems inevitable that the truth will soon come out, and Melanie has teased that the reveal will be heartbreaking.

“It’ll not only be a betrayal of her husband Rich,” she explained, “but the double betrayal of her close colleague and friend. In the ED you have to trust each other and there’s a camaraderie, as you’re working on life and death situations together.

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“[Siobhan and Stevie] have formed a bond recently, which will make the reveal more horrifying. Stevie’s a lot younger than Siobhan so it’s the age difference as well, and she is not feeling very confident in herself at the moment.”

She continued: “But at the same time, it’s three adults who are trying to navigate this difficult situation. None of them are bad people. I don’t think Rich is a bad person – he hasn’t been sleeping around, he just fell in love with Stevie.”

As well as dealing with her own personal turmoil, Siobhan has also been supporting nurse Cam this series, as he comes to terms with the fact that he was sexually abused as a child by his former mentor Jamie.

Amid Cam’s fallout with fellow nurses Jodie and Rida, he has leant heavily on Siobhan after telling her the truth, and Melanie says that Cam sees her as a “mother figure”.

Cam’s story took a major turn in this week’s episode (August 24) when Jamie’s car was run off the road by fellow victim Bobby and he crashed over a steep gorge. As Jamie’s life hung in the balance, Siobhan advised Cam to take this moment to speak to his abuser – but it didn’t go to plan.

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“[Siobhan] can’t get answers from Rich,” Melanie reasoned, “so she tells Cam to take this moment when Jamie is between life and death and get the answers he needs. But that doesn’t work at all, and Jamie just sticks the knife in further and twists things.”

Jamie died shortly after this, but Cam’s ordeal is far from over as he wrestles with the guilt of not being there for Bobby earlier – and Melanie confirms that Siobhan’s unwavering support will continue in the coming weeks.

“I enjoy playing these emotional threads,” she said. “And that’s why Casualty is so important. It is a family show, and it’s important that these stories get told.”

But what is next for Siobhan, as the current series of Casualty comes to a climax in the coming weeks?

“It won’t end well,” Melanie said. “It’ll get much, much worse before it gets better. But I’m still filming, I haven’t been bumped off!”

Casualty airs on Saturday nights on BBC One and now streams first on BBC iPlayer, where episodes are released at 6am on the day of transmission.

Read more Casualty spoilers on our dedicated homepage

Casualty has worked on Cam’s storyline with Survivors UK and We are Survivors – both of which offer resources and support for sexual abuse survivors and their loved ones.

If you’ve been affected by the issues raised in this story, you can access more information from Rape Crisis England and Wales, which works towards the elimination of all forms of sexual violence and sexual misconduct, on its website or by calling the National Rape Crisis Helpline on 0808 802 9999. Rape Crisis Scotland’s helpline number is 08088 01 03 02.

Readers in the US are encouraged to contact RAINN, or the National Sexual Assault Hotline on 800-656-4673.