For five decades, American agencies have stockpiled information on UFOs. So did their counterparts behind the iron curtain.

Soldiers, scientists and spies all paint a disturbing picture of the KGB's secret campaign. The UFO encounter that almost sparked a nuclear war.

The pair of MiG fighters that tried to shoot down a UFO - both jets blown out of the sky! Stunning proof that the Soviets recovered something not from this earth! Amazing film footage smuggled out of Russia.

This exclusive investigation into one of the most compelling events of our time is hosted by Roger Moore.