Two young girls who, in the mid-19th century, began hearing spirits making knocking sounds in their New York home. This quite literally started the popularity of séances to obtain spirit raps in the US, and helped to get going the religion of Spiritualism, part of which is the belief that you can communicate with the deceased through the help of a medium. Later they became professional performers, sank into alcoholism, admitted they were fakes and had created the knocks through non-paranormal means, and later recanted their admission.