The series is about police officer Ho Tin Kwong, who on a stormy day found his dad's old cell phone. Unbelievable even to him, after lightning struck, Tin Kwong discovers that the phone was able to contact his dad that lived 20 years ago before he died in an unsolved crime case back then. With the help of his father, they re-open cold cases and solve them together through the 20-year time span difference.