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unforgotten ep 5© Photo: ITV

Why did Nicola Walker leave Unforgotten as DCI Cassie Stuart?

The actress exited her role on the ITV drama in season four

Emmy Griffiths
TV & Film Editor
Updated: February 7, 2025
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Unforgotten season six might be back for a new season on Monday evening, but fans will be sad knowing that adored TV star Nicola Walker won't be back as DCI Cassie Stuart.

Sinéad Keenan's DCI Jessie James serves as the new detective in town to keep DI Sunny Khan company. Although she'll never replace Cassie, fans loved watching her in season five - and this season is set to be no different - but what happened to Nicola's character, and why did she quit? 

WATCH: Meet Jessie James

Chatting about the reasons why she left, the Last Tango in Halifax star told Radio Times: "Chris Lang and I had been discussing the storyline for Cassie since the first series. By the time we got to her nervous breakdown in series three, we were already talking about where that story might naturally go, so her sudden death was very much a joint decision."

Unforgotten Sunny and Cassie in season four© Photo: ITV

She added to TV Insider: "Chris and I were always interested in looking at the cost of being involved with these sorts of cases that we all love watching on television. Cassie does not have superpowers. She’s an ordinary person who’s really good at her job, and it took her to the place of having an emotional breakdown."

Sinéad Keenan and Sanjeev Bhaskar© ITV
Sinéad Keenan and Sanjeev Bhaskar

She joked: "I’m not on social media, but when the final episode went out, I almost wanted to join Twitter to tell everyone that I didn’t walk away from the show, nor did they ask me to leave. It was simply that Chris and I thought it was a fantastic, impactful story. I love the irony of this brilliant woman dying an accidental death that wouldn’t be investigated in a show about complicated investigations ... We hoped people wouldn't feel we were being cruel by serving up this incredibly sad story." 

Sinéad Keenan and Sanjeev Bhaskar as DCI Jess James and DI Sunil 'Sunny' Khan in Unforgotten© ITV
Sinéad Keenan and Sanjeev Bhaskar as DCI Jess James and DI Sunil 'Sunny' Khan in Unforgotten

Will Nicola ever return to Unforgotten? 

Although we would love to see Nicola back on the show, we think that the nature of Cassie's exit makes her return pretty much impossible - unless she is set to return as a ghost - or in a prequel! The actress has been incredibly busy since leaving the show, starring returning to The Split, Annika, Marriage and Mary and George. 

Nathan (STEPHEN MANGAN), Hannah (NICOLA WALKER) in The Split Barcelona© BBC / SISTER
Nicola in The Split Barcelona

What is happening in season six? 

Excited for season six? The synopsis reads: "The series begins when suspected human remains are uncovered on Whitney Marsh – Jess and Sunny are immediately called to the scene, abandoning their evening plans to Jess’s husband’s chagrin. Dr Balcombe’s analysis reveals that the remains are relatively recent and suggest a grim conclusion: the body was placed there already dismembered.

Sanjeev Bhaskar and Sinéad Keenan as DI Sunil 'Sunny' Khan and DCI Jess James© ITV
Sanjeev Bhaskar and Sinéad Keenan as DI Sunil 'Sunny' Khan and DCI Jess James

"With this insight, Jess and Sunny intensify their search certain that other body parts may not be far away."

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