Two off-duty police officers are killed when a bomb explodes in a bowling alley. A police informer (Paolo Olivarez), who had come to warn them, arrives too late and though slightly injured is able to hobble away. A Bronx detective demands that Kojak allow him to help bring in his informer; they trace him to his sister Marinella's in New Jersey. Back in New York, the bombers booby trap Paolo's apartment; when that fails, they notify him that they have kidnapped his sister to ensure his silence. Knowing that they want to kill him, Paolo offers to trade himself for her freedom. Kojak learns of his plans and where the bombers' HQ is; he faces a hostage situation involving Marinella, and Paolo is frantic. Will Kojak call their bluff?