Casualty: Mistletoe and Rum begins with Fletch rushing to finish a phone call to his family, so he can get back to the nurses' Christmas party. As he hangs up he meets homeless but proud Tyron, who tries to convince a dubious Fletch the importance of making the most of every minute with his young children. In the pub Charlie is thanking all of the nurses for their work this year, just as everyone hits the dance floor. Spotting an opportunity Fletch and Tess step outside the pub for some air, where cheeky Tyron asks Tess for a kiss under the mistletoe. But the combination of diabetes and living on the street sends Tyron into a hypoglycemic coma leaving the nurses battling to keep him alive. Will it be a happy Christmas for everybody?