Another spin-off series is in the works, and while "Chicago Justice" is not yet in full production, the "Chicago P.D." season 3 episode 21 will serve as its backdoor pilot. The title of the next episode is "Justice" and it will center on a complicated situation involving one of their own and someone from squad commander Hank Voight's past.

The trouble for the team will start when a man open fires the patrol car of Roman and Burgress. When Roman is hit by a bullet, Burgress runs after the assailant. Burgress fires at the assailant who was later identified as a high school student and leaves with him an injury. While Burgress fires upon seeing that the student is aiming at her direction, no gun will be found on the scene of the crime.

The report will cause an uprise as the situation will implicate Burgress to be liable for misconduct. Assistant State Atty. Peter Stone is assigned to her case. However, Voight and the rest of the team will be forced to conduct their own investigation to help Burgress since Atty. Stone sent Voight to prison in the past.

Executive producer Matt Olmstead spoke to Entertainment Weekly regarding the upcoming episode. He said the story is inspired by a real event that occurred in Philadephia where two cops sitting in their patrol car were ambushed and the shooter ran away. The story won't follow the real events though as the event only serves as their jump-off point for the episode.

Will helping their friend by involving themselves in an unauthorized investigation put the whole team in jeopardy? Is the lawyer assigned to Bugress really out to prove her innocence? How will the team get through a case involving one of their own when the situation is under the public's watchful eyes?

Watch "Chicago P.D." Wednesdays, 10 p.m., on NBC.