"They seem to be very quick, sporadic responses," said Barbara McBeath of the Ghost Investigators Society about the strange Electronic Voice Phenomena (EVP) recordings made in places like an old frontier prison in Montana. Appearing on Thursday night's show with fellow G.I.S. member Brendan Cook, the two played a variety of goose bump inducing samples they had captured on their recent expeditions. While the words of the non-visible entities aren't always clearly intelligible, what comes through "is their emotion and personality," said McBeath.

For example, in the audio they made while walking down to the basement of a mausoleum, just the strangely drawn out word "go" is heard, but the intonation is rich in the sound of dread and disdain. Cook and McBeath explained that there are generally two types of ghostly activitiesâ€"an intelligent haunting, which is interactive and a residual haunting which is often repetitive and non-reactive. Many of their EVP recordings seem to be of the first kind, with the voices seemingly responding to something that a G.I.S. member is saying or doing. Occasionally some of the voices they record are astonishingly clear. "I almost had the key," wistfully intoned a recording made at the Deer Lodge prison.