The Outer Limits (New Series)
From Within
S2 E13:
Mentally challenged Howie (Neil Patrick Harris) is the last unaffected person in a small town overrun by a parasitically-induced madness. Howie is desperate to save his sister Sheila (Christine Hirt), but deprived of her guidance for the first time, he must rely on his own strength to overcome the madness.
Starring
Christianne Hirt, Patrick Stevenson, Gabrielle Miller