Episode 18 is the 1110th episode of Casualty and the 18th episode of the 33rd series. It was preceded by Episode 17 and followed by Episode 19. The episode was directed by Matthew Evans and written by Katie Douglas, and was the first episode to air in 2019.
Base knocks on Iain's door and asks him to celebrate Mia's birthday with him. They go to the seaside to pay their respects, and, knowing that she would've liked it, Base leaves a giant teddy bear on the beach for a child to find. He asks Iain if they could go back to his house to talk, but Iain decides to take Base to the pub instead. As Iain finishes his first pint of lager, a man named Gregor barges past him, irritating him. Iain follows him to the toilets and demands an apology, but Gregor dismisses him, prompting Iain to start a fight. As the brawl continues into the bar, Gregor's friend Caitlin tries to break up the fight, but he unintentionally pushes her into a table of pint glasses. Once the paramedics arrive, Ruby is shocked to find Iain, and he claims that Gregor instigated the fight.
In the ED, Iain receives treatment for his injuries, and Base tells him that it looked like he deliberately tried to get beaten to a pulp. After Base leaves to meet up with a friend of his, Iain is discharged. As he leaves the hospital grounds, he tries to apologise to Gregor, but he tells him to shove it. However, blood starts running down his legs, and he collapses. It transpires that he had sustained an injury to his groin while he was in the army. Iain empathises and tells him that other people will understand if he gives them the chance. That evening, Iain leaves the ED and finds Base waiting for him. Base tells him that he is going down the same dark path as Mia and says that he doesn't want to let him reach the same point as her. Iain dismisses his concerns and calls Mia a selfish loser who only ever wanted a razor blade out of life; Base walks away.
After catching Jade and Marty reading a magazine on the job, Louise tells Marty to work with her in resus, but he leaves her unimpressed when he makes callous remarks about a patient. Jade manages to get him into trouble again after she accidentally glues a patient's head to a pillow, and the two fall out when Marty claims that she makes him look bad. Marty tries to tell Louise that Jade is to blame, but she tells him to prove that he deserves to be in the ED. He later proves his worth by assisting in performing a cricothyroidotomy, but he continues to argue with Jade. That night, after Jade answers an ad for a spare room in a shared house, she and Marty are not happy to find out that they're living together.
Elsewhere, Charlie and Duffy agree to keep the news about their separation to themselves. However, Robyn presents them with a hand-made doily, and, when Duffy can't bear to keep it, Charlie throws it in the bin. Robyn later finds it and asks Charlie what is going on between him and Duffy, and he tells her that they have split up.