Professor Parkins, a rational scholar on holiday at Burnstow, discovers an ancient bronze whistle among the ruins of a Templar preceptory. Curious, he blows it, unwittingly summoning a terrifying presence that takes shape in the bedclothes of his hotel room. Despite his disbelief in the supernatural, Parkins faces a nightmarish encounter—only saved by the timely intervention of Colonel Wilson, who disposes of the whistle.