The Secret of Skeleton Island (1966) - Front cover of ''The Secret of Skeleton Island''.The Mystery of the Whispering Mummy (1965) - Front cover of ''The Mystery of the Whispering Mummy''.The Secret of the Crooked Cat (1970) - Front cover of ''The Secret of the Crooked Cat''.The Mystery of the Nervous Lion (1971) - Front cover of ''The Mystery of the Nervous Lion''.The Secret of the Phantom Lake (1973) - Front cover of ''The Secret of the Phantom Lake''.The Mystery of the Silver Spider (1967) - Front cover of ''The Mystery of the Silver Spider''.The Mystery of the Shrinking House (1972) - Front cover of ''The Mystery of the Shrinking House''.The Secret of the Phantom Lake (1973) - Front cover of ''The Secret of the Phantom Lake''.The Secret of the Crooked Cat (1970) - Front cover of ''The Secret of the Crooked Cat''.The Secret of the Haunted Mirror (1974) - Front cover of ''The Secret of the Haunted Mirror''.The Mystery of the Talking Skull (1969) - Front cover of ''The Mystery of the Talking Skull''.The Mystery of the Moaning Cave (1968) - Front cover of ''The Mystery of the Moaning Cave''.The Mystery of the Whispering Mummy (1965) - Front cover of ''The Mystery of the Whispering Mummy''.The Mystery of the Coughing Dragon (1970) - Front cover of ''The Mystery of the Coughing Dragon''.The Three Investigators - Front cover from the ''The Three Investigators'' series.