The Mystery of the Talking Skull (1969) - Front cover of ''The Mystery of the Talking Skull''.The Mystery of the Coughing Dragon (1970) - Illustration for ''The Mystery of the Coughing Dragon'' by artist Harry Kane.The Three Investigators - Front cover from the ''The Three Investigators'' series.The Mystery of the Stuttering Parrot (1964) - Front cover of ''The Mystery of the Stuttering Parrot''.The Secret of the Haunted Mirror (1974) - Front cover of ''The Secret of the Haunted Mirror''.The Mystery of the Coughing Dragon (1970) - Illustration for the Danish release of ''The Mystery of the Coughing Dragon'' by artist Peter Madsen.The Mystery of the Shrinking House (1972) - Front cover of ''The Mystery of the Shrinking House''.The Mystery of the Dancing Devil (1976) - Front cover of ''The Mystery of the Dancing Devil''.The Mystery of the Whispering Mummy (1965) - Front cover of ''The Mystery of the Whispering Mummy''.The Mystery of the Vanishing Treasure (1966) - Front cover of ''The Mystery of the Vanishing Treasure''.The Mystery of the Flaming Footprints (1971) - Illustration for the Danish release of ''The Mystery of the Flaming Footprints'' by artist Peter Madsen.The Mystery of the Magic Circle (1978) - Front cover of ''The Mystery of the Magic Circle''.Alfred Hitchcock: The Three Investigators - Front cover from the ''The Three Investigators'' series.The Mystery of the Deadly Double (1978) - Front cover of ''The Mystery of the Deadly Double''.The Mystery of the Singing Serpent (1972) - Front cover of ''The Mystery of the Singing Serpent''.