A man pricks his finger while tending to an exotic plant and is rushed to the ER, where he is diagnosed with a bacterial infection before a worm-like parasite emerges from his mouth. As the infection spreads throughout the ER, the parasite is exposed to a genetic growth stimulant, which causes it grow to monstrous proportions and terrorize the hospital.

Steve Railsback
as Det. Jim Bishop

Gwynyth Walsh
as Dr. Rachel Carson

John Vernon
as Roger Levering

Joe Flaherty
as George Baker

Robin Duke
as Sandra Baker

Susan Anspach
as Dr. Judith Glass

Don Lake
as Elliot Jacobs

Helen Hughes
as Marwella

Sandy Webster
as Fred

Joy Coghill
as Dede Wilkens