Dorothy Martin isn’t overly enthusiastic when her husband, retired police detective Alan Nesbitt, invites her to accompany him to a conference in Cambridge, picturing cramped student accommodation. But St Stephen’s turns out to be recently renovated, and, bolstered by en suite facilities, Dorothy is looking forward to exploring the historic and beautiful city. It is not long, though, before disaster strikes: lost in the maze of college buildings, Dorothy stumbles into a laboratory... and is shocked to find what looks like a pool of blood on the floor. She flees, to fetch help, but when Alan checks it out, there is nothing to be found. Was she mistaken? Or has a terrible crime been committed? Dorothy, who can never resist a puzzle, determines to find out.