Two detectives communicate through a walkie-talkie to solve a cold case. One detective exists in the present day; the other detective exists 15 years in the past.
The story continues from the Japanese SIGNAL drama series. In 2021, a limousine taxi driver causes an accident on a highway, and a high-level government official dies in the accident. The cold case investigation unit, including Kento Saegusa and team leader Misaki Sakurai, have doubts about the case. Meanwhile, in 2009, administrative officers die consecutively in car accidents. The police announce these deaths as accidents. Takeshi Ōyama believes that these deaths were not the product of simple accidents. At 11:23 pm, a walkie-talkie turns on and makes a connection between the future and past. Kento Saegusa and Takeshi Ōyama face the threat of bioterrorism.
