As Holmes and Watson struggle through the Christmas-shopping crowds, they must catch this most dastardly and un-Christmassy of villains, while sneakily trying to purchase each other's Christmas presents (they are in the world's least-secret Secret Santa, after all). Meanwhile, with the museums of London refusing to return cultural artefacts to their countries of origin, someone is taking matters into their own hands, and stealing back what was stolen. Are the cases connected, and could an ancient air fryer of demonic power hold the key to the mystery of the murdered Santas? And more importantly, can you prepare a whole Christmas dinner in an air fryer? Whether you can or not, Dr Watson's going to give it a jolly good try. Ho Ho Holmes!