The murder of Angela Hathall was extremely well planned. The only clue left was a single fingerprint with an L-shaped scar. The detective in charge, Reg Wexford, suspects that Angela's husband Robert Hathall killed his wife. But one question troubles Wexford most of all. Who is the mysterious woman Wexford is sure Hathall is seeing? Does she have an L-shaped scar on her finger?