Mark, Tom, Allison, and Linda, four college employees, were determined to defeat the aliens. Doing so, however, required traveling through time--into the past to learn about the origins of the extraterrestrials and how to conquer them, and into the future to see what effects the aliens have had on society.
Scares occurred, and several nearly died, but order was restored and life at college returned to normal. For now, at least.