Next airing Wed May 2, noon ET

Alien Roadkill

Nat Geo joins the search for an unidentified "highway beast" in Minnesota whose image still haunts residents to this day. And in Canada, one of the world's top salmon rivers experiences a record run, the largest in a century - it's a fisherman's dream. Experts search for an explanation for the sudden influx of marine life. Villagers in Southern Africa are stumped by round patches of sand that stretch over a thousand miles of landscape. Could the phenomenon symbolize a message from higher beings?