L. M. Greenspan, the head of ailing Climatic Studios, gave producer Garney Hendrickson, five days to get a major movie in the can - and Climactic out of it. Impossible? Not with Professor Hewett's miraculous presto chango time machine, the answer to a Hollywood producer's prayer. Nipping back to AD 1,000 with a whole film crew and two glam stars, Barney sets out to prove that the Vikings discovered America five hundred years before Columbus…