Professor and Mrs. Moriarty each take on a small case to fill the time before their next play opens. They place a bet on who will finish first. James will find out if three old soldiers have been cheated of their discharge pay. Angelina must find a missing servant, presumed to have been poached.

But as they start asking questions, things take a dark turn. They uncover corruption at the heart of a circle of Army officers. A man is murdered, a friend is blamed, and Sherlock Holmes is sent to catch him. The Moriartys must use all their courage and ingenuity to save their friend, stop the loathsome crimes, and put the killer behind bars.