The fourth season focuses on Jess and Nick's friendship in the wake of their break up, Schmidt and Cece's friendship after the dismissal of Buster, Winston's journey towards becoming a cop, and Coach's growth as a teacher.
Schmidt tutors Jess in the not-so-fine-art of dating via mobile apps.
In Chinatown, on the day of his birthday, Mark Chao is killed by the chief of a gang, Tony Wong, without any apparent motive. The spirit of Mark contacts Piper and Phoebe asking for help because if he is not buried in a short time, Yama, the gatekeeper of the gates of hell would collect his soul.
Piper attempts to help Mark and the two develop feelings.
Meanwhile, Winston is desperate to make a good impression on his fellow police cadets, which backfires when Nick, Coach and Cece show up at a party thrown by fellow officers.
Jess' dad arrives with his new girlfriend, who happened to be Jess and Cece's high-school rival.