LONDON—The University of London's Senate House Library is one of the finest academic research institutions in England. On a recent day, a lecture room in the imposing Art Deco building was filled with the world's pre-eminent authorities on a talking mongoose named Gef.

In a nation long fascinated by the supernatural, the case of Gef the talking mongoose stands out as one of the most bizarre in British paranormal history. Though he is largely forgotten, a small but obsessive band of researchers refuses to let Gef go.

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