There is both excitement and dismay in Llanfair when a new French restaurant opens in an old chapel. The glamour owner, Madame Yvette, tries to win over the locals and everything seems to be going well until a string of arson fires plagues the village. One night the restaurant burns down, and a body is found in the rubble.

Constable Evans joins Sergeant Watkins in follow a trail of clues that leads them to the South of England, and then to France, and finally to the conclusion that a dangerous killer is loose in Llanfair.