Duncan MacDonald, a 19th-century Royal Canadian Mountie, has to escort a group of Cree Indians back to their above-the-border reservation. His guide in this endeavor is the not-too-trustworthy half-breed Natayo.

A giant asteroid is heading toward Earth so some astronauts disembark from a nearby space station to blow it up. The mission is successful, and they return to the station unknowingly bringing back a gooey green substance that mutates into one-eyed tentacled monsters that feed off electricity. Soon the station is crawling with them, and people are being zapped left and right!