"Bah Humbug" is the 1019th episode of Casualty and the 15th episode of the 31st series. It was preceded by "All I Want for Christmas Is You" and followed by "New Year, New Me, New You". The episode was directed by David Beauchamp and written by Dominique Moloney.
The events of the episode take place on 24 December, with the exception of the pre-main intro sequence which picks up directly from the previous episode the day before. Following the episode's transmission, the BBC released Casualty's winter trailer, which featured various upcoming moments of early 2017.
The next day, it's Christmas Eve and spirits are high in the department. However, Seb is dreading facing Dylan following their awkward encounter the night before, and even gets him a present in an attempt to make amends. However, Dylan carries on as normal like nothing had ever happened, keeping professional.
Ryan goes out shopping to get Duffy a present at a local store, which is booming with business. The store's manager Larry is busy entertaining the reporters, who've come to document the Christmas rush. However, when two women, Linda and Irene, become argumentative over a doll, things soon escalate. Chaos ensues which results in several shelves falling down, merchandise breaking, looting, a Christmas tree falling on Ryan and a window being smashed. Local store worker Rob is worried as his son Toby has been crushed by a falling TV. All six people in the shop are admitted to the ED.
Connie continues struggling with Grace, and is gradually helping her to start walking at home. Jacob tries to get her to give Grace a break for Christmas, but she refuses to give up. At work, Connie treats the two women who were arguing over the doll. When it becomes apparant that it's a stolen good, she confiscates it. Noel expresses concerns to Louise over the fact his hours have been cut as a result of the new automated check-in system in the ED.
Duffy becomes worried about Ryan's condition, and this only worsens when he collapses in reception. After various tests and a CT scan, Charlie suspects that he's simply putting it on for Duffy's attention which he later admits to. Although Duffy is angry, she speaks to Paul and although he wants her to go back to New Zealand, says that he only wants her to if she'll be happy. Charlie also pressures her to tell Ryan the truth.
Meanwhile, Rob accompanies Toby into the ED and Seb begins treating him. However, when Larry catches sight of Rob he is furious that he left the shop. He then instructs him to fire all of the security personnel for not doing their job properly or he'll fire him. Rob reluctantly agrees to, fearing for his own job, but Louise is concerned about Larry's treatment of his staff.
Seb is intent on clearing beds and although Louise raises concerns about Toby, he dismisses them as he'd not told him about the symptoms himself. He checks him over as per Rob's request but finds nothing and assumes that he's okay. However, when Toby gets out of bed to see Larry with Louise, he collapses and is taken back to cubicles. Dylan discovers a rash on Toby's stomach and is angry with Seb for not being thorough enough. Louise inadvertently reveals to Max that Robyn is pregnant and although she's worried about how he'll react, he takes it well when she tells him that it's good news.
Connie eventually takes the doll to the two women and gives it to Irene as she deems her to be more deserving of it. However, when she overhears her speaking to the doll she realises that she doesn't have a daughter after all. Connie's later impressed when Irene does the right thing and gives the doll to Linda, which also inspires her to consider Jacob's idea about getting the puppy for Grace. Louise surprises Noel with a train ticket to Manchester so he can visit Honey for Christmas and give her a present.
Duffy agrees to go for dinner with Duffy even after he screws up the divorce papers. However, midway through she realises that she can't go ahead and presents him with the papers once again, pleading him to let her go. He accepts and signs the papers, realising that it's what she wants. He also suspects correctly that she's fallen for Charlie. Lily gives Seb a gift for him to give to his father from her.
Jacob dresses up as Santa Claus for Grace, as Connie presents her with the new puppy and she's delighted. Once again they're all together as a happy family and they're happy to see Grace smiling again. Dylan confronts Seb in the staff room and gives him his final chance, threatening to fail him in January if he doesn't get his act together. Shortly after, Elle notices him crying in the staff room and he claims that Dylan tried to kiss him, not the other way around. She is surprised and shocked by the allegations he's making against Dylan.
Just as it begins to snow, Duffy meets Charlie outside the ED and gets down on one knee and proposes to him. Although she doesn't have a ring, Charlie finds a ring from a packet of sweets and presents it to her. By then some of the staff have collected outside as they congratulate them on their engagement.