A space patrol find an alien world surrounded by a strange mist. They are fired on by the inhabitants and plan to retaliate, but realize too late that they were trying to keep them from the deadly mist surrounding the planet.
Three young historians set out to prove the New World was settled by mariners who came from Africa on rafts. However, they not only travel across the ocean, but also to the past, landing among the ancient Aztecs. Fleeing them, they dive over a waterfall and end up back in the present, but with evidence of their time travels.