Ran receives a message from Kisaki Eri through a messaging app saying she's been captured by some bad guys. But two Eri's are participating in the group chat, and the other claims it's just a joke. Ran doesn't know which is the real Eri. Two hours earlier, Eri was kidnapped by a group of three men and taken to an abandoned building. Eri stole one of the men's phones, escaped from them, and sent Ran a message asking for help from inside a locker. Conan and friends search for Eri, but...

Conan, Mouri, and Ran witness Nichiuri Sports reporters arguing at a restaurant. One leaves the restaurant and accidentally takes the other's travel mug with him. That night, a body is found on the riverbank. The cause of death is poisoning by cyanide mixed into the coffee in his travel mug.