A deadly situation unfolds as a terrorist faction known as the Red Siamese Cats invades a secure laboratory, wiping it out with a powerful explosion. They broadcast a chilling online message claiming they have seized a dangerous bacterium and announcing themselves as the Red Siamese Cats, a group that had been eradicated a decade earlier.
Conan Edogawa, Kogoro Mori, Ran Mori and the Detective Boys are invited by Jirokichi Suzuki to board his airship for a staged confrontation with the famed jewel thief Kaito Kid. The plan: bait Kid into stealing the precious Lady Sky as the airship nears Osaka. Aboard the vessel, alongside the police and crew, are four media professionals—Takamichi Fujioka, Masaki Mizukawa, Kasumi Nishitani, and Junpei Ishimoto—whose presence adds a layer of tension and scrutiny to the spectacle.
Inside the smoking room, a waitress discovers an ampoule bearing the Red Siamese Cats emblem hidden beneath a couch, foreshadowing the danger to come. Conan, recalling Ran’s past misgivings about a flying airship being a UFO, asks Doctor Agasa to keep that memory in check. A waiter overhears the conversation from the shadows, hinting that something bigger is at play.
As the airship tour unfolds, Ran diverges to get a closer look at Lady Sky and unexpectedly encounters Kid, who is wearing a disguise. She believes she’s found the thief and subdues the masked guest, threatening to hand him over to Ginzo Nakamori. Kid unmasks himself, feigning the identity of Shinichi Kudo to placate her, claiming she once mistook the airship for a UFO.
Meanwhile, the crew begins to notice a rash spreading among some of the adults—Fujioka is affected and knocked unconscious, while the waitress with the rash is placed in quarantine along with the unconscious journalist. Conan splits from the main group to reunite with the Junior Detective League, who are exploring the ship’s attic, where an unidentified assailant appears to open the roof, allowing the Red Siamese Cats to take control.
The group in the lobby is later forced to watch as the rogue team seizes Lady Sky and issues a dark warning: if resisted, bombs will detonate or a second ampoule will spread the contaminant. Conan discovers four bombs in the attic and foils their plan, while Heiji Hattori attempts to read the villains’ true objectives and foresees a calculated assault on key locations, including a major city-building complex, to maximize panic and chaos.
As the ship sails toward Nara, the Red Siamese Cats announce their larger scheme over the internet, while Mizukawa’s rash symptoms cause concern and Nishitani laments the Detective Boys’ absence, a moment the conspirators exploit to tighten their grip. Ai Haibara informs Conan through a Detective Badge that the group is targeting him, but the message is interrupted when a short-haired waitress—revealed to be part of the conspiracy—strikes Ai and reveals her involvement.
A dramatic reversal happens when Conan is hurled from the airship’s windows by the leader, only to be saved by Kaito Kid. Heiji deduces the Cats’ goal would be to crash the airship into no fewer than three landmarks and unleash the bacteria across the city. Conan alerts the police and coordinates with a helicopter team to rejoin the airship, while the remaining bombs are tracked and disarmed.
The investigation leads to a startling revelation: the Red Siamese Cats are a team of foreign mercenaries hired by Takamichi Fujioka, using the non-existent bacterium as a cover. Nishitani and Ishimoto are revealed to be Fujioka’s co-conspirators, while the two embedded bombs in the lobby are meant to secure their escape and prize Lady Sky. When Fujioka attempts to eliminate Conan, the airship glides beneath a bridge and Conan's belt is used to launch a tethered soccer ball, wedging the craft and collapsing the plan. Fujioka falls into the ocean, and his accomplices are knocked unconscious.
Kid reenters the scene, frees Ran from the railing, and departs with Lady Sky. As they stand in the moonlight, Ran—believing Kid to be Shinichi—asks him to surrender to the police. Kid agrees to be captured only if she shares a kiss, but the moment reveals a truth Ran senses: the thief’s behavior is not that of Shinichi. When Conan finally confronts Kid, Ran’s later reflection makes it clear she recognizes the difference between the fearless flirtation and the familiar conduct of the true Shinichi, leaving the moment open in her memory as the jewel slips away.
