A feature-length special to conclude the anniversary celebrations, which stretches from a grey, damp and drizzly London all the way to the sparkling beauty of idyllic Saint Marie. A wealthy shipping magnate is found dead at a Christmas party. Things get stranger when a man in London receives a mysterious Christmas card connected to the victim's death. Danny John-Jules makes a return as charismatic Officer Dwayne Myers, with special guests Mathew Baynton, Juliet Stevenson, Stanley Townsend, Jocelyn Jee Esien, Anthony Calf, Tessa Bonham Jones, Elizabeth Tan, Tariq Jordan and Sara Cox joining the regular cast