Santa Louisa's Halloween celebrations are derailed when a masked killer dressed as a clown strikes in the entertaining new Mary McGill dog mystery.

Mary McGill and her cocker spaniel Millie get the fright of their lives on Halloween when they hear gunshots coming from the bank and the robber, dressed in a clown costume, points his gun at them before fleeing the scene. Mary is horrified when she discovers Police Chief Dan Dunham has been shot in the shoulder and a woman has been killed. Why would the clown shoot an ordinary citizen?

Mary soon learns that the victim is Victoria Witherspoon, a local woman who owned a sewing shop and must have recognised the clown costume - because she made it herself. With Dan in hospital and unable to investigate, can Mary and Millie unmask the savage killer clown before he strikes again?