The Secret of Terror Castle (1964) - Front cover of ''The Secret of Terror Castle''.The Mystery of the Magic Circle (1978) - Front cover of ''The Mystery of the Magic Circle''.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 Mystery of the Singing Serpent (1972) - Front cover of ''The Mystery of the Singing Serpent''.The Mystery of the Headless Horse (1977) - Front cover of ''The Mystery of the Headless Horse''.The Mystery of the Silver Spider (1967) - Front cover of ''The Mystery of the Silver Spider''.The Mystery of the Talking Skull (1969) - Front cover of ''The Mystery of the Talking Skull''.The Secret of the Crooked Cat (1970) - Front cover of ''The Secret of the Crooked Cat''.The Secret of Skeleton Island (1966) - Front cover of ''The Secret of Skeleton Island''.The Secret of the Haunted Mirror (1974) - Front cover of ''The Secret of the Haunted Mirror''.The Mystery of the Deadly Double (1978) - Front cover of ''The Mystery of the Deadly Double''.The Mystery of the Silver Spider (1967) - Front cover of ''The Mystery of the Silver Spider''.The Mystery of the Moaning Cave (1968) - Front cover of ''The Mystery of the Moaning Cave''.The Mystery of the Stuttering Parrot (1964) - Front cover of ''The Mystery of the Stuttering Parrot''.