As teenage skateboarder Alex (Gabe Nevins) hops freight trains with a stranger named Scratch (Daniel Liu), a security guard spots them and tries to forcibly remove them. In the scuffle, Alex strikes the guard with his skateboard, knocking him in the direction of another train, which kills him. Alex tosses his board into the river, but soon he and other skaters are called in for questioning by Detective Lu about a recovered skateboard that has been linked to the scene of the crime.