Grey conducts a triple murder investigation, the last murder committed gives him some clues to the murderer and that the victim may have known his killer. He devises a plan to identify the guilty party, who is a scary psycho and he is captured.

In India, a British detachment finds itself surrounded in a village by invisible enemies. An officer is assassinated, then another. The adversary seems very well informed. By who ? A group of twenty men who had gone to seek help were annihilated. An American reporter will force the mysterious spy to denounce himself.