After Detective Liang Renjie’s fiancée, Ruoyun, dies in a bizarre accident, he receives a mysterious phone call telling him to download an APP called CODE. The APP gives him clues to solve cases but then demands him to return the favors. Du Zixin, a journalist, tells him the APP is involved in many fatal accidents. With a hacker called Hank, the trio decide to unravel the truth behind CODE.

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