The Three Investigators - Front cover from the ''The Three Investigators'' series.The Mystery of the Silver Spider (1967) - Front cover of ''The Mystery of the Silver Spider''.The Mystery of the Deadly Double (1978) - Front cover of ''The Mystery of the Deadly Double''.The Mystery of the Coughing Dragon (1970) - Front cover of ''The Mystery of the Coughing Dragon''.The Mystery of the Laughing Shadow (1969) - Front cover of ''The Mystery of the Laughing Shadow''.The Mystery of the Green Ghost (1965) - Front cover of ''The Mystery of the Green Ghost''.The Mystery of the Stuttering Parrot (1964) - Front cover of ''The Mystery of the Stuttering Parrot''.The Mystery of the Shrinking House (1972) - Front cover of ''The Mystery of the Shrinking House''.The Secret of Terror Castle (1964) - Front cover of ''The Secret of Terror Castle''.The Secret of the Crooked Cat (1970) - Front cover of ''The Secret of the Crooked Cat''.The Mystery of the Screaming Clock (1968) - Front cover of ''The Mystery of the Screaming Clock''.The Mystery of the Whispering Mummy (1965) - Front cover of ''The Mystery of the Whispering Mummy''.The Mystery of the Death Trap Mine (1976) - Front cover of ''The Mystery of the Death Trap Mine''.The Secret of Shark Reef (1979) - Front cover of ''The Secret of Shark Reef''.The Mystery of the Coughing Dragon (1970) - Illustration from ''The Mystery of the Coughing Dragon'' by artist Harry Kane.