Watch Poltergeist: The Legacy full episodes online.
Synopsis: A group known as The Legacy battles the forces of evil and the paranormal in an effort to keep humanity from being destroyed. The team is made up of various members, including brilliant scholar Dr. Derek Rayne, psychiatrist Dr. Rachel Corrigan, researcher Alexandra "Alex" Moreau and former Navy SEAL Nick Boyle. The members of The Legacy search for and uncover a secret world of terror while trying to defend the world against evil and darkness. The first three seasons aired on Showtime before moving to Sci-Fi Channel for its final season.
More info: IMDB, Wikipedia