eenager Harriet Farmer is attacked in woods on her way to elope with boyfriend Finn Robson and left in a coma. Finn vanishes and a year later, as the annual Bishopwood chess tournament begins, Harriet wakes up with temporary amnesia. The chess club president, unpopular writer Edward Stannington is murdered, his sole heir being his dippy aunt Vivian. Barnaby learns that Stannington is the father of a young chess prodigy whom he has disowned and was out to discredit his chess rival, Alan Robson, Finn's father, the millionaire creator of a computer chess game. Furthermore unhappily-married hotelier Arthur Potts wanted the victim to invest in his ailing business and was refused. After Harriet's father is also murdered her kindly doctor, Laura Parr, and Barnaby take the girl to the woods where she was attacked to see if she can recall the events of the previous year. Her memories eventually lead to the unmasking of the killer, a face from the past of one of the families with a revenge plan more deadly than any Sicilian Defence.

Résumé de IMDb.com