Veteran detective Cham works with rookie cop Will to hunt down the city's serial killer. The investigation leads them to a lair littered with dismembered female limbs, and an ex-con who killed Cham's wife and child years ago...

Set in the 1980s, troubled youth Chan Lok-kwun accidentally enters the Walled City, discovers the order amidst its chaos, and learns important life lessons along the way. In the Walled City, he becomes close friends with Shin, Twelfth Master and AV. Under the leadership of Cyclone, they resist against the invasion of villain Mr. Big in a series of fierce battles. Together, they vow to protect the safe haven that is Kowloon Walled City.

电影发展基金下的「串流平台内容开发计划」第一阶段评审工作现已完成，选出十个入围计划进入第二阶段开发完整剧本，而十部作品中，其中一部正是《九龙城寨信一传》。 另有消息指《信一传》会由郑保瑞做监制、李子俊做导演、岑君茜做编剧。