Nagano PD's Kansuke Yamato and Yui Uehara are alerted that a researcher has been attacked at an observatory in the Yatsugatake Mountains. During the investigation, Kansuke starts feeling a strange discomfort in the eye he injured during an avalanche 10 months prior. Meanwhile, Kogoro receives a call from his former colleague Sametani, who claims to be investigating the avalanche that Kansuke was involved in. But before Sametani can share his findings, he is assassinated right before Kogoro and Conan's eyes. Determined to uncover the truth, Kogoro travels to Nagano himself, while Conan launches his own investigation. While in Nagano to investigate the killing of Sametani, Conan and Kogoro discover the avalanche is linked to a robbery that happened 8 years before. But when Detective Kansuke becomes the target of a mysterious assailant, the stakes rise sharply. Can Conan unravel the web of secrets and stop the killer before it's too late?