It’s been almost two weeks since NBC’s “Chicago P.D.” aired an episode in Season 4. Fortunately, the series is back this week with an episode that will see the police department’s finest try to bust a drug ring that targets college students.

Season 4, episode 5 will see the team investigate a mysterious backpack that has washed up in the lake. When Hank Voight (Jason Beghe) opens it, he finds a pack of deadly opiates known as fentanyl. This fatal drug is responsible for killing many people in Chicago. Not long after, the team finds the body of a college student.

In order to bust the drug ring and get information from a smuggler, Officer Adam Ruzek (Patrick John Flueger) poses as a college student. The Intelligence Unit learns that a dealer that goes by the name of Red knows the source of the fentanyl supply in Chicago. Hence, Ruzek pretends to be a drug addict looking for a quick fix. Fortunately, the transaction goes smoothly and Red gets arrested.

Elsewhere in Season 4, episode 5 of “Chicago P.D.,” tensions run high in the department when Mouse (Samuel Hunt) reveals that he wants to reenlist in the army rather than continue to work as the tech genius of the Intelligence Unit. He asks Voight for a favor – drop his felony record so that he can sign up to serve his country again.

Of course, Mouse’s friend Detective Jay Halstead (Jesse Lee Soffer) is vehemently opposed to his idea since they served together in the army in the past. And it wasn’t pretty. Can Halstead convince his friend not to go back to that difficult life?

In another part of Chicago, Patrol Officers Tay (Li Jun Li) and Burgess (Marina Squerciati) find a child covered in blood on a street.

Halstead’s brother Will (Nick Gehlfuss) will stop by the department to meet him and warn him of the dangers of the new drug that is claiming many lives at the hospital.

“Chicago P.D.” Season 4, episode 5 premieres on Wednesday, Oct. 26 at 10 p.m. EDT on NBC.