Like most new parents, Linda and Peter Pratman (Darlanne Fluegel and Martin Neufeld) have been looking forward to the arrival of their new baby. And when their little boy finally comes, they're beside themselves with joy. It turns out, however, that the infant they brought home isn't theirs; the newborn they'd hoped to cradle was switched with another, a little terror who grows up with a murderous bent that neither parent can handle -- or stop.