The Last Call (1970)

Today is legendary radio DJ Harry Cunningham's final day working at WQRX FM radio before he makes the transition to XM. He came into work expecting to just do a clip show, takes some calls, and say his goodbyes. However, when a strange caller demands he unearth a dark secret live over the radio, Harry refuses. One by one everyone in the station is being picked off by this strange caller who only has one request...play the tape or DIE.