It always feels like Casualty is entering a new era when Holby’s emergency department gets a new clinical lead. While Siobhan has been holding down the role temporarily, in the first episode of new boxset ‘Internal Affairs’, viewers met the new boss, Flynn Byron – played by Call the Midwife favourite Olly Rix.

Flynn was introduced as a special forces medic with a young family, who was hiding some big secrets, including that he had an affair in the military with a woman called Amber. After a clandestine meeting with his former lover, the pair were involved in a horrific road accident and were both rushed to hospital.

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Much of the episode was filmed from Flynn’s point of view as the team tried to save his life, an innovative way to kick off this new boxset and introduce this mysterious character. But just as innovative is the two-month time jump that followed – and there is lots to unpack.

After recovering from his serious accident, Flynn strolled into the ED and dropped a bombshell on his old medical school mate Stevie, explaining that he is the new clinical lead and pledging to make big changes in Holby when he starts next week.

This could spell bad news for Tariq, as from his hospital bed Flynn observed him making some crucial mistakes when treating another patient. Tariq is excited about the big changes in the ED next week, but will Flynn remember his incompetence and hold a grudge?

It was also revealed that Flynn’s father-in-law is surgeon Russell, played by Cold Feet’s Robert Bathurst in a guest role this series. When Russell discovered that Flynn was a patient in the ED, he feared that his daughter Claire had died in the accident. But he soon realised that Flynn had been with another woman and was having an affair.

Russell decided not to break his daughter’s heart, but his knowledge of Flynn’s betrayal sets up an exciting dynamic, especially now they will be working together.

Another huge talking point is Stevie’s shock discovery that she is pregnant, after falling ill during a shift at work. Two months later, it appears that she has kept this major news to herself, but next week she reveals to Faith that she is expecting a baby – and her late lover Rich, Siobhan’s husband, is the father.

It’s an interesting new story arc for Stevie, who is still grieving for the man she had an affair with, and has said that she isn’t interested in having a child. But things might not be quite as they seem and there are some twists and turns in the weeks to come, with Elinor Lawless continuing to deliver a superb performance.

The flashforward also set up another unexpected story, with Dylan spotting Ngozi walking into an Alcoholics Anonymous meeting held for NHS staff. Ngozi panicked when she saw her colleague and pretended that she had accidentally walked into the wrong room, but it is clear that she is secretly attempting to tackle a very real problem.

Having been played by the formidable William Beck since 2011, Dylan is arguably Casualty’s most nuanced and carefully crafted character. It is heartening to see his alcoholism and recovery continue to be acknowledged in recent series and it would be a beautiful full circle moment for him to be able to help Ngozi through a similar struggle.

Ngozi herself has been a great addition to the show, and her surprising friends-to-lovers plot with Nicole has been lovely to watch play out. But we still don’t know a lot about her life, aside from her loving relationship with her son Obi, so it will be great for the show to flesh out her character more in this series.

The new trailer for this boxset of episodes sets up all of this drama and more, including an intense rivalry between Rida and Nicole on Russell’s surgical team, Iain and Faith’s wedding, more struggles for student paramedic Indie and a dramatic ambulance crash in the ED that spells danger for the whole team.

Casualty’s current boxset format is working so well because it allows different characters to shine in each series, and it highlights that the show has trust in its entire cast to take centre stage. For example, it will be a joy to see more from brilliant newcomer Naomi Wakszlak as Indie, and for Adesuwa Oni and Sarah Seggari to tackle some big stories as Ngozi and Rida.

Not only does ‘Internal Affairs’ look genuinely thrilling, but it seems that the next set of episodes will give viewers a deeper insight into characters both old and new, and will also explore some fresh dynamics between some of the ED’s most beloved staff members.

It’s going to be an exciting 12 weeks in Holby…