Hazel and Daisy are spending the Christmas holidays not at boarding school, but in snowy Cambridge, where Daisy's brother Bertie is studying. Hazel is looking forward to the romantic university town, cozy libraries, and inviting tea houses – and to reuniting with Alexander, with whom she has been friends since the murder on the Orient Express. However, danger lurks on the dark stairs of Maudlin College. Three days before Christmas, a terrible accident occurs. At least it seems to be an accident – until the detective duo takes a closer look and discovers: It was murder! A search for clues begins, during which Hazel and Daisy face obstacles from adults once again, receive detective support, and ultimately find themselves in the crosshairs of the murderer. They must use all their skills to track down the culprit.