Hunter’s archenemy, a Soviet agent and killer known as Bluebird, is suspected of killing an American who betrayed the Soviets after leaking American nuclear secrets to them. Bluebird murders a succession of informants before Hunter can contact them, usually leaving a razor-sharp throwing star in each victim's body but on one occasion sabotaging a victim's parachute. The murders lead Hunter and Marty to a Soviet plot to discredit an American nuclear-powered electric plant design. This was the first episode of the weekly series, which used the new premise of Hunter and Marty being counterespionage agents.