Conan, Kogoro, and Ran take a trip to Ishikawa Prefecture's Kanazawa to meet with a tourism agency. They have asked for Kogoro's help with the Kaga Hyakumangoku Mystery Tour city revitalization event to be held in the Kanazawa.

The anime special celebrates the 20th anniversary of Gosho Aoyama's original manga, and it recounts a previously untold story from Conan's past.

Conan, Ran, and Ai visit a public bath, where Conan slips, loses consciousness, and is abducted by two shady figures named Tatsu and Kondou. He wakes up imprisoned and suffering from memory loss, unable to use his detective skills. Meanwhile, the adults—Mouri Kogoro, Ran, and others—begin their search, piecing together clues as sinister criminal plots converge around Conan's disappearance. The mystery escalates around a looming bomb threat, prompting high-stakes drama to rescue him.