A famous actor is sent to his death from a high window; eye witnesses say he was pushed by an invisible hand, thus mimicking another murder committed in the same house more than fifty years earlier. Three local girls have also died in similar inexplicable fashion, propelled from the top of Wish Tor, a rocky outcrop. Is there an invisible creature roaming the sinister and forbidding landscape of Dartmoor? Or is there a human agency behind the murders...