A would-be killer plays a cat-and-mouse game with the Saint. But who is the mysterious avenger?The world is undoubtedly full of ungodly ones who have found, to their cost, that the Saint, Simon Templar (ROGER MOORE), will not hesitate to bring them to justice. There is, therefore, a large field of possible avengers on which to draw when trying to guess who might be responsible for the death threats he is now receiving.The first warning comes in a box which he finds in his car when accompanied by the glamorous American journalist Mary Ellen Brent (SUZANNE LLOYD), who is writing a feature on the Saint. The box contains a snake - harmless in itself, but accompanied by a note: 'This is just the beginning... I have more surprises for you and the final one -the best of all - will be the death of the famous Simon Templar.' Needless to says, it is unsigned. Any suggestion that it is a hoax is soon dismissed when the Saint has a narrow escape from being run down by a car, and then a mysterious telephone call from a man who says: 'I want to come to your funeral, Mr. Templar. I want you dead....'This is followed by an attempt to give the Saint an electric shock, but the man tampering with a lamp in his apartment is caught in the act when Simon returns unexpectedly and recognises him as a small?time muscle-man named Charlie Mason (TERENCE RIGBY). Charlie says he has been given a hundred pounds to do the job, but doesn't know who by. He promises Simon that he will let him know if he hears anything more and keeps his word when he telephones Simon to give him an address. Simon goes to the address -and finds Charlie Mason dead. He has paid for his double-cross on both the Saint and the mystery man - but has helped Simon in an unexpected way because his girl-friend Laura Carlton (LINDA MARLOWE) comes up with some information. But she, too, pays the penalty and is shot dead. The Saint is now not so concerned with the threats against himself but with trac watch