Task: Question Generation
Input (English): The Phantom Thief Kid sends a heist notice, warning of another heist. The police deduce that his next target is a recently discovered FabergÃ© egg, which Suzuki Modern Art Museum in Osaka will display on August 22. The night of the heist, Kid steals the egg and flies off, and Conan and Heiji give chase. However, in the middle of the chase, an unknown assailant shoots Kid in the right eye, and Kid apparently falls into the sea to his death. After recovering the egg, the police fruitlessly search for Kid's body.The next day, Conan, Ran, and Kogoro board a boat to Tokyo. They meet Natsumi Kousaka, whose great-grandfather worked in FabergÃ©'s factory. She shows them a part of a sketch of two eggs and a key, which were found among her late grandmother's momentos. Conan suspects that the person who shot Kid is on the ship. That night, Ryu Sagawa, a freelance photographer covering the press with news of the egg, is murdered, shot in the right eye in the same fashion as Kid. Soon after his body is discovered, Inspector Megure with officers Takagi and Shiratori arrives by helicopter to inspect the crime scene. At first, they suspect Serena's father's servant, Mr. Nishino, but the police and Conan conclude the culprit is Scorpion - a mysterious killer who always shoots his victims in the right eye. A missing lifeboat hints that Scorpion has escaped, and the boat's passengers go to Yokosuka Castle, which holds Scorpion's next target: the second egg.While exploring the castle, the group stumbles across secret passages beneath the castle. As they traverse the tunnels, Inui, an art dealer, pursues a shadowy figure he sees in one of the tunnels, and is shot by a silenced handgun. Delving farther into the tunnel, they find a coffin with a corpse clutching the second egg. Suddenly, the two eggs are snatched away.Conan deduces that Scorpion is Seiran the historian. She shoots her victims in the right eye to avenge her ancestor, Rasputin, whose body was found with an eye missing. Seiran attempts to kill Conan with her last bullet, but the bullet ricochets off the bulletproof glass on Conan's glasses Conan had Agasa install. As Conan kicks a rock, she reloads and is about to fire when a playing card knocks the gun out of her hands. Conan then knocks her out with the rock. Shiratori appears and carries Seiran out. Conan figures Shiratori is Kid in disguise. Back in Beika, Conan is about to confess to Ran that he's Shinichi, only to be interrupted by Kid, who is disguised as Shinichi and distracts Ran. Kid then disappears in a flurry of pigeons.
Output (English): Question: What does the group stumble upon while exploring the castle ?, Answer: Secret passages.