In this British production based on Edgar Wallace's "Dark Eyes of London," a crooked insurance underwriter (Lugosi) dons a phony mustache and dubbed-in voice to masquerade as a head of a home for the blind, where he murders people in order to collect their policies. He accomplishes this by binding the victims in straitjackets, drowning them in a tank of water and dumping them on the banks of the Thames. A Scotland Yard inspector risks his life to aid a young girl who has stumbled too close to the truth about the scheme.