The decades spanning story of two very different policemen who rise to power in Hong Kong during British rule, and end up at odds with both organised crime groups and the anti-corruption unit vowing to bring them down.

Feng (Shawn Yue) is a former undercover cop whose post-assignment life has begun to rapidly disintegrate. Feng and former triad brother Fai (Sam Lee of Gen-X Cops) are caught using cocaine, and the ensuing melee leaves a police detective dead, with Fai fingered as the culprit. Fai must go on the run, but he no longer trusts Feng, who he believes may be leveraging their brotherhood for advancement in the police ranks.

Kaoru has Xeroderma Pigmentosum (XP), and is not allowed to be exposed to sunlight. She sleeps during the day and is active at night. She busks every night in front of a station playing guitar. Outside her bedroom window, she spots a high school boy with a surfboard. She watches him and his friends visit the ocean every morning, before going to sleep. One day, she introduces herself to him without letting him know about her illness. He is Kji Fujishiro (Takashi Tsukamoto) When her cousin drags her home, they sit by her window while they watch Kji meet his friends. Kaoru explains everything, and her cousin notes that she probably goes to the same school as him, and offers to spy on him for her.