Casualty has released the new trailer for their next boxset, Internal Affairs, and it’s got our pulses racing!

Here’s everything you need to know…

Casualty Internal Affairs — release date

The opening episode of Casualty’s 12-part miniseries Internal Affairs airs on BBC One on March 15 2025 at 8.30 pm on BBC One. It will also be available to air on BBC iPlayer from 6 am.

The main players in Internal Affairs

The Casualty characters under the microscope in the new boxset are:

• Newly appointed clinical lead Flynn Byron (Olly Rix)
• Consultant Stevie Nash (Elinor Lawless)
• Recently engaged paramedic Iain Dean (Michael Stevenson) and advanced clinical practitioner Faith Cadogan (Kirsty Mitchell)
• Nurse Rida Amaan (Sarah Seggari) and junior doctor Nicole Piper (Sammy T. Dobson) are in for a testing time, as they work closely with senior surgeon (Russell Whitelaw) and surgical registrar Sean Redmond (Seth Somers).
• Also in the spotlight are trainee paramedic Indie Janowski (Naomi Wakszlak), Rash Masum (Neet Mohan) and Dylan Keogh (William Beck) in scenes that make us impatient to watch this new chapter in Casualty.

Please note: There are major Casualty spoilers beyond this point.

Internal Affairs — big reveals

Clinical lead Flynn Byron — played by Olly Rix

The introduction of Olly Rix as army medic Flynn Byron sets the tone for the new 12-parter.

“As the new Clinical Lead Consultant at Holby City ED, Flynn joins the NHS fresh from a tour of duty. He’s a man with a purpose, and with a fierce resolve to make a difference,” explains the Casualty press release. “He faces the challenge of instilling change in a system weighed down by bureaucracy, all the while grappling with the trauma he has experienced and a deception that threatens to be his undoing.”

The trailer opens with Flynn telling Stevie Nash that he’s the new clinical lead – the position she was hoping to land.

It then hints at a power struggle with his father-in-law Russell Whitelaw (more on him below), who has been instrumental in Flynn securing his new role at Holby ED.

Also seen in the trailer: Flynn caught up in a shocking car accident, the medic reacting furiously after being on HEMS duty, and a physical attack on fan favourite, consultant Dylan Keogh!

Surgeon Russell Whitelaw — played by Robert Bathurst

“Internal Affairs will also feature acclaimed actor Robert Bathurst in the guest role of Russell Whitelaw,” explains the BBC press release before adding that the character is: “a top-tier surgeon who has commanded the operating room for years with his unmatched skill and domineering personality.”

In the trailer Russell can be seen asserting his control over Flynn, who doesn’t take kindly to his father-in-law’s interference, but appears to be unable to stop it for yet-to-be revealed reason.

It also looks like Russell has recruited ED nurse Rida Amaan and junior doctor Nicole Piper to his theatre team…

Rida Amaan — played by Sarah Seggari

If you’ve been watching Casualty for a while and thinking that Sarah Seggari was due a meaty storyline, Internal Affairs is must-see viewing, as it’s revealed Rida will be working alongside Russell and Nicole in the intense environment of life and death surgery.

The narrative in the trailer suggests that Rida begins this competitive chapter of her career impressed by Russell and defensive of him initially. At some point it appears that she begins to question his methods as well as those of her boyfriend Sean.

Adding to this theory are a series of meaningful and loaded looks between the characters involved, a rooftop scene with Nicole and Rida where she channels The Godfather and reveals her intentions to: “Keep my friends close and keep my enemies even closer”, and the closing scene where she’s distressed and gasping for breath while dressed in bloody surgical scrubs.

It’s also worth remembering that Rida is a woman with a strong moral compass and has history as a whistleblower…

Stevie Nash — played by Elinor Lawless

Stevie is deep in grief when Internal Affairs opens, following the death of firefighter Rich Walker.

In the trailer, close friend Faith is seen comforting Stevie, but it looks like there’s a double dose of trouble in store for the consultant who is seen holding a pregnancy test and being arrested!

Stevie voices that: “Someone is doing this to get at me.”

Fans’ first thoughts may be that, if this is the case, the culprit is nurse manager Siobhan McKenzie (Melanie Hill) who remains devastated and furious that Stevie had an affair with her husband Rich. But who else would like to exact a seemingly twisted revenge on the Holby ED doctor? Your thoughts are welcome in our comments section above!

Other big Internal Affairs storylines to keep an eye out for

• In this jampacked trailer, Faith Cadogan and Iain Dean are seen in their wedding finery entering a reception room filled with friends and family.
• Indie Janowski reaches a personal breaking point. (Aside: Did you notice the identity of the actor playing the stabbed patient she hurts? Let us know in the comment section!)
• The ED’s most levelheaded and mildmannered doctor Rash Masum (Neet Mohan) attacks an unknown man!*
• An ambulance crashes into the department, causing serious damage.
• Holby experiences a terrifying riot.
• And Flynn attacks Dylan Keogh. But why?