While fishing, Conan and with the Detective Boys spot a sniper shooting a balloon tied to a remote controlled boat on the river. This sniper is held at gunpoint by other men.
Koichi Yamabe, Eri
The Detective Boys go to find these men but when they get there, the gunmen have left.
Conan finds a calculator under a small concrete block which he believes was left behind by the sniper. Kogoro, Ran and Conan, joined by the Detective Boys, find a stretch of road that mirrors the river used for the test. They call the police and find out that the sniper, Koichi Yamabe, and his girlfriend, Eri, were recently reported missing. However, while waiting for the criminals to arrive at the supposed sniping spot, Conan realizes that the numbers on the calculator, when read upside down, spell out a different message entirely.
The sniper left behind a calculator with the numbers 3,135,134,162 on the screen.
The sniper's test was held at about one o'clock in the afternoon.
When Ran suggested that the numbers 162 might be a road, Kogoro declared that the shape of the river might be similar to the bends of the road for the sniping site.
When Conan accidentally sees the numbers upside down, the numbers can be read as "291 Heisei E".
The sniper that Conan saw was Koichi Yamabe, a police officer and former rifle marksman of Japan's Olympic team. He and his girlfriend, Eri, were abducted by the criminals while on vacation. The criminals held Eri hostage so that Koichi Yamabe would work for them.
When the criminals don't arrive at the site on Saitama Route 162, Conan and the Detective Boys try reexamining the code. As Mitsuhiko punches the numbers into his calculator, Conan accidentally sees that when upside down, the numbers can read as "291 Heisei E". The decoded message means the one o'clock train on February 9th of the Heisei Express train. The shape of the river turns out to mirror a double-curve in the train tracks of the Express. The criminals want Koichi to shoot someone inside the train and the balloon was just an accuracy test.
The kidnappers forced Koichi to snipe the District Attorney for Eri's life.
Conan sneaks into the helicopter taking Inspector Megure to the train line. Before Koichi can assassinate the target, Inspector Megure instructs the pilot to swoop down and distract the criminals. Conan uses his Power-Enhancing Kick Shoes to kick his helmet towards one criminal before he can shoot Koichi. Koichi is able to take down the remaining criminals and save Eri from harm.
The criminals were former members of a gang whose leaders were caught in a sting operation last year. They wanted revenge on the district attorney who set up the operation, and planned to shoot him while he was on his way back from a vacation with his family.