Poltergeist: The Legacy - Season 2 - Eps 14: Lullaby
Kat and some of her friends experiment with an Isis board and manage to summon a presence of some kind or other. Kat collapses but is fine the next morning. She doesn't talk much about what happened and keeps quite about what they were really doing, afraid of getting herself and her friends into trouble. Later the presence forms itself as a woman who appears inside or outside their rooms and sings lullabies to them. The ghost seems to be passive, that is until one of the girls disappears overnight!
About Poltergeist: The Legacy

Title: Poltergeist: The Legacy
First Air Date: 1996-04-21
Last Air Date: 1999-11-12
Status: Ended
Rating: 6.1/10 (from 33 votes)
Language: EN
Seasons: 4
Total Episodes: 88
Network: Showtime
Genres: Sci-Fi & Fantasy
Production Companies: Trilogy Entertainment Group
Synopsis
The adventures of the members of a secret society known as the Legacy and their efforts to protect humankind from occult dangers.
Cast

Derek de Lint
Derek Rayne, Ph.D.

Martin Cummins
Nick Boyle

Helen Shaver
Rachel Corrigan, MD

Robbi Chong
Alexandra Moreau

Kristin Lehman