This was in tv, but I am confident it was not an episode of a tv show. It was in the mid to late seventies, and it was in color. The movie starts off with a young man who lives in a mansion with his family. There is a strange room that is always kept locked, because entering it will kill you or turn you insane, but may give you some secret knowledge. His first attempt to enter the room results in him almost dying but he wakes up on the couch. There were flashes of a lot of bizarre things the room is showing him. The second attempt is a success, but he realizes he has died but is now immortal. This sort of cult develops around him. And there are many depictions of followers committing suicide to gain immortality. The cult runs amock in the town, meanwhile the main guy is pressuring his girlfriend to take her life as well to gain immortality. She resists, towards the end of the movie, she is cornered by him and the other followers in a graveyard and handed a knife and is being forced to do this. However before that can happen all of the followers turn into stone pillars.