The Secret of the Crooked Cat (1970) - Front cover of ''The Secret of the Crooked Cat''.The Mystery of the Coughing Dragon (1970) - Front cover of ''The Mystery of the Coughing Dragon''.The Secret of Skeleton Island (1966) - Front cover of ''The Secret of Skeleton Island''.The Mystery of the Shrinking House (1972) - Front cover of ''The Mystery of the Shrinking House''.The Mystery of the Green Ghost (1965) - Front cover of ''The Mystery of the Green Ghost''.The Secret of the Haunted Mirror (1974) - Front cover of ''The Secret of the Haunted Mirror''.The Mystery of the Death Trap Mine - Front cover of ''The Mystery of the Death Trap Mine''.The Mystery of the Coughing Dragon (1970) - Front cover of ''The Mystery of the Coughing Dragon''.The Mystery of the Moaning Cave (1968) - Front cover of ''The Mystery of the Moaning Cave''.The Mystery of the Silver Spider (1967) - Front cover of ''The Mystery of the Silver Spider''.The Three Investigators - Front cover from the ''The Three Investigators'' series.The Secret of Terror Castle (1964) - Front cover of ''The Secret of Terror Castle''.The Mystery of the Flaming Footprints (1971) - Front cover of ''The Mystery of the Flaming Footprints''.The Mystery of the Coughing Dragon (1970) - Front cover of ''The Mystery of the Coughing Dragon''.The Mystery of the Moaning Cave (1968) - Front cover of ''The Mystery of the Moaning Cave''.