Buck Rogers in the 25th Century (1979)

S1E6 The Plot to Kill a City (1)

Following the assassination of an intergalactic assassin by a Defense Directorate agent, the remaining assassins seek vengeance against New Chicago. To infiltrate their ranks, Buck pretends to be one of them, but his true identity is quickly revealed. Now, he faces the dual challenge of evading the assassins while racing against time to prevent them from blowing up the city's matter/antimatter energy facility.