This week’s Casualty delivers the kind of high-stakes drama fans thrive on, with Stevie Nash teetering on the edge of becoming the ultimate bridesmaid from hell just as Faith Cadogan and Iain Dean prepare to walk down the aisle. Episode 11 of the gripping 12-part saga Internal Affairs, airing Saturday 31 May on BBC One, piles on the tension as Stevie’s absence looms over Faith’s big day, Russell Whitelaw doubles down on his scheming, Ngozi Okoye flirts with disaster, and Indie Jankowski faces a heart-wrenching test of loyalty. With every storyline threatening to unravel friendships, relationships, and careers, the episode sets up an explosive climax ahead of the finale. Casualty has always thrived on chaos in the ED and beyond, but this instalment raises the stakes even higher as weddings, betrayals, and moral dilemmas collide in devastating fashion.

Faith is a nervous wreck on the morning of her wedding, though her fears have nothing to do with cold feet. Instead, she’s tormented by the thought of standing at the altar without her maid of honour, Stevie Nash, at her side. Their recent falling-out has left Faith desperately reaching out to Stevie, only to be met with radio silence. Groom Iain, sensing the tension, decides to take matters into his own hands and secretly heads to Stevie’s flat to convince her to attend. What he doesn’t know is that Stevie is battling a storm of her own. Reeling from menopausal symptoms following her hysterectomy and haunted by the looming start of chemotherapy, Stevie drowns out the world with loud music and a cold shower, only for tragedy to strike when she faints under the freezing water. In true Casualty fashion, the timing is cruel: Iain pounds on the door, unaware of her muffled cries for help. Just as he is about to leave, fate intervenes, the music dips, and he hears her distress. The paramedic’s instincts kick in, and on his own wedding day, Iain once again plays the hero.

The rescue only deepens the emotional turmoil. Once Stevie is warmed up and out of danger, she confesses her intention to skip her maid of honour duties altogether, telling Iain he should hurry to his own ceremony without her. But Iain refuses to abandon her, coaxing Stevie into opening up about her upcoming chemotherapy and the fear she has kept bottled inside. Through compassion and determination, he convinces her to find the strength to stand by Faith’s side. For a moment, it feels as though everything might just work out. Yet the reprieve is short-lived. At the reception, Stevie drowns herself in alcohol, her pain bubbling to the surface as she self-destructs in front of the very couple whose love she should be celebrating. What should have been a joyous union spirals into chaos as Stevie’s reckless behavior threatens to taint the day forever. The fallout from her actions could leave lasting scars on her friendship with Faith and Iain, raising the haunting question: will Faith’s wedding be remembered for love, or for betrayal at the hands of her best friend?

As if the wedding drama weren’t enough, other characters face equally devastating crossroads. Ngozi Okoye turns up to the reception without her girlfriend Nicole Piper, and the absence leaves her vulnerable to temptation. After an emotionally draining shift, Ngozi’s judgment wavers, and she edges dangerously close to a decision she may regret for the rest of her life. Her relationship with Nicole has already been fraught with tension, and what unfolds at the wedding party could push it past the point of no return. Elsewhere, trainee paramedic Indie Jankowski is thrust into a dilemma that no young medic should face. Her father, Samuel, forces his way into her new world, leaving Indie torn between protecting her biological family and standing by her paramedic family. It’s a choice with no easy answer, and whichever side she picks, the consequences will be profound. For Indie, the night that was supposed to be a celebration quickly becomes a crucible that will define her loyalties and her future.

Back at the hospital, the stakes take on a darker shade. Russell Whitelaw, facing the threat of investigation after his assault on nurse Rida Amaan, turns to blackmail and bribery in a last-ditch bid to save himself. His target is his son-in-law Flynn Byron, whose witness statement could seal Russell’s fate. Flynn, caught between his marriage and his conscience, becomes ensnared in a chilling web of manipulation. Meanwhile, Rida is forced to relive the trauma of Russell’s attack during the HR inquiry, her strength tested as the man who wronged her tries to twist the narrative in his favor. The question looms: will Flynn betray Rida and side with Russell to protect his marriage, or will he stand firm against a powerful surgeon intent on burying the truth? With Stevie spiraling, Ngozi tempted, Indie torn apart, and Russell scheming, Casualty’s latest instalment serves up everything fans crave — heartbreak, suspense, betrayal, and the relentless reminder that in Holby, the line between celebration and catastrophe is perilously thin.