As part of a study of the dynamics of belief in groups, some social psychologists once infiltrated several small cults.  Among the groups observed was one led by a woman who was given the fictitious name of Mrs. Marion Keech.  The events described really took place.  Mrs. Keech claimed to have made contact with extraterrestrial beings, and she regularly revealed to her followers what she claimed were messages from her contacts.  One day, she said that her contacts had told her that they were going to destroy the world.  She even gave a specific day on which this was supposed to happen.  These extraterrestrial beings also told her, she claimed, that they would rescue her, and anyone else who wished to be saved, if they would wait at a designated location.  On the appointed day, Mrs. Keech and her followers were at the designated place.  The day wore on, but the world did not end.  Finally, Mrs. Keech informed her followers that she had received a telepathic message from her contacts informing her that they had decided to spare the world from destruction because she and her followers had been so strong in their faith that the rescue would indeed take place.  The psychologist undercover observer reported that the assembled followers returned to their homes apparently strengthened in their belief that Mrs. Keech was indeed in contact with powerful extraterrestrial beings.