Blake and Mortimer head to the United States to investigate the mysterious circumstances surrounding the discovery of a 177-year-old body, which appears to have died very recently. The body is that of a Scottish Major, Mortimer's forebear, who was leading a British military expedition to the US in 1777, when he was swallowed up by a strange multi-coloured light beam shining down from the sky. Blake and Mortimer must fight men in black armed with green laser guns and soldiers emerging from the past in order to save Earth from complete obliteration.