Suzuki Jirokichi receives a letter from Kaito Kid which reveals that Kid plans on opening Jirokichi's impenetrable safe, the Iron Tanuki. The letter however is not written in Kid's usual style raising the ideal that an imposter is after Jirokichi's safe. Sonoko invites Ran, Kogoro, and Conan to Jirokichi's house. After examining the security of the safe, Kaito Kid's card, in its usual style, is found confirming Kaito Kid's plan to open the safe. Conan suspects that Kaito Kid is one of the three newly hired workers of Jirokichi. Jirokichi however countinues to proclaim it to be the work of an imposter, causing Conan to suspect Jirokichi's behavior.

The nearly hired maid and adviser inform Conan of Jirokichi's strange behavior. They reveal that after dinner, two places are always missing and Jirokichi always brings his cane with him to the safe. Jirokichi asks the maid for a hand and they head to his room. Jirokichi leaves with his bodyguard for a drive. Shortly after, an unconscious Jirokichi is found tied up and his room and a note of Kaito Kid is found on the safe. This causes the whole police force that are guarding the safe to abandon their position and chase after "Jirokichi". Conan meanwhile enters the room with the safe revealing the maid was Kaito Kid in disguise. Conan reveals the first message by "Kaito Kid" was actually done by Jirokichi asking for Kaito's kid assistance. Conan also reveals Jirokichi purposely placed suspicion on himself in order to clear the area of cops so Kaito Kid can open the safe. Inside the safe is revealed to be Jirokichi's dog, Lupin.