After a construction worker is killed by insects burrowing into his brain, Sam and Dean investigate the town's history and find that the new housing development is being built on sacred Indian land. The Indians put a curse on the land after their reservation had been ravished and destroyed. Sam and Dean must find a way to survive and kill the deadly swarm of bees, locusts, spiders and beetles.

Sam and Dean investigate an abandoned sanitarium and discover that when the hospital was open, the patients held a revolt against the cruel and unusual punishments inflicted by the head doctor. While the brothers search the premises for four lost college students, the tortured spirits cause them to go insane, turning Dean against Sam.