Henry Twyst, eighteenth Duke of Chellingworth, is convinced his mother is losing her marbles. She claims to have seen a corpse on the dining-room floor, but all she has to prove it is a bloodied bobble hat. Worried enough to retain the women of the WISE Enquiries Agency -- one is Welsh, one Irish, one Scottish and one English -- Henry wants the strange matter explained away. But the truth of what happened at the Chellingworth Estate, set in the rolling Welsh countryside near the quaint village of Anwen by Wye, is more complex, dangerous, and deadly, than anyone could have foreseen.