The madness begins when Captain Orange and his three nieces are killed in a carriage accident. The only clues? A tall man seen near the Captain's house, and a broken mirror found in the Captain's breast pocket. Next, Janet Calthorp of King's College, London, tumbles to her death as she makes her way to her lover's bedroom, the victim of a tripwire. The clue? A broken mirror found in said lover's boudoir. So it is little surprise that, when the dead body of Juan Thomas de Jesus-Lopez is discovered in a ruined lighthouse, the only clue found is a broken mirror. "Mirror, mirror, on the wall," muses Superintendent Lestrade, "who's the guiltiest of them all?" He is to find out.