Kaito Kuroba is an ordinary teenage student whose father is frequently absent. Following his father's mysterious death, Kaito learns of his secret identity as a renowned international criminal known as International Criminal 1412: the Phantom Thief. He discovers that his father was murdered by a mysterious organization for refusing to help them retrieve the "Pandora Gem," a mystical stone said to shed a "tear" during the passage of a specific comet (often called the 'Volley Comet'), which grants immortality upon consumption. Kaito vows to stop the organization from achieving immortality and assumes his father's identity as he embarks on a quest for the gem. His only clues regarding the gem's location are that it glows red under the full moon and that it is a doublet: a gem hidden within a larger one. Consequently, it must be a relatively large gem with a bizarre history, always stored in a place that never receives moonlight. He therefore researches and steals famous priceless gems with odd histories from incredibly well-defended locations, always returning them after the very next full moon.