Perched on a cold, windswept island in the middle of San Francisco Bay, Alcatraz was designed to be inescapable. And for most of its prisoners, it was. But even after the federal penitentiary closed in 1963, something appears to have stayed behind. Guards, tourists, and park rangers have reported unexplained sounds and shadowy figures in the corridors long after closing. What occupied these cellblocks in life, seems to have no interest in leaving after death.