Mouse (Samuel Hunt) may no longer be a part of the team as he strongly wants to re-enlist in the army. More on this in the upcoming episode 5, titled "A War Zone," of "Chicago P.D." season 4.

Although the people around Mouse do not entirely agree with the idea of him re-enlisting in the army, it looks like he has set his eyes on it and will do everything to make it happen. If his plans push through, it will be an added burden for his best friend, Halstead (Jesse Lee Soffer). The team counts on Halstead to convince Mouse not to go through his plan. However, he is known to make decisions without considering anyone else's opinion.

If he leaves the team, it will also add another weight to the unit since Detective Antonio Dawson (Jon Seda) will also be transferred to another post. Since "Chicago" is a huge TV series franchise, Seda will be transferred again as a series regular to another spin-off series, the freshman "Chicago Justice."

In a previous interview with TV Guide, executive producer Matt Olmstead had teased that the current season will test Mouse and Halstead's friendship, which could be affected by Mouse's interest in being re-enlisted.

"Halstead is adamant about him not going back over. Which has much more to do about Halstead than Mouse," Olmstead said. "It culminates in a really moving story about that relationship, that friendship between Halstead and Mouse, the loyalty, the promise that they would look after each other over here."

The team's next case will be about the multiple drug overdoses around the city. They find out that the drug called Fentanyl is the culprit of these deaths. They will hunt down the dealers and will end up following a drug ring inside a college.

"Chicago P.D." season 4 airs Wednesdays at 10 p.m. on NBC.