Colonel Pete Moore (Glen Ford) is commander of the Whitney Radar Test Group, which has been experiencing electrical difficulties aboard its aircraft. To ferret out the problem, he sends a four-man crew on Flight 412. Shortly into the test, the jet picks up three blips on radar, and subsequently, two fighters scramble and mysteriously disappear. At this point, Flight 412 is monitored and forced to land by Digger Control, a top-level, military intelligence group that debunks UFO information. The intrepid colonel, kept in the dark about his crew, decides to investigate the matter himself.