'Chicago P.D.' season 4 episode 15 spoilers: Intelligence unit gets caught in a gang war; Ruzek is demoted to patrol duty?

An old case and old feelings are reopened in the next episode of "Chicago P.D." Will Ruzek's (Patrick John Flueger) return affect Rixton's (Nick Wechsler) stint with District 21's Intelligence Unit in any way?

The previous episode of NBC's crime drama saw Ruzek's return from the undercover assignment he asked to be sent to when his old flame, Burgess (Marina Squerciati), joined the team. But his time away has also given him a chance to think about his place in Intelligence as well as in Burgess' life. And although the kiss they shared may seem like a clear indication of rekindled romance, are the two of them really ready to go down that path again?

On top of this, an old, unresolved case gets reopened when the victim's grieving father comes to Chicago looking to hire a hitman to take care of his daughter's killer. When Lindsay (Sophia Bush) gets tipped about it, Intelligence sends Olinsky (Elias Koteas) in as an undercover hitman-for-hire in an episode titled "Favor, Affection, Malice or Ill-Will."

The case was never solved due to the lack of evidence to make an arrest. However, when the team reinvestigates and gets close to exposing the original gangbanger, things quickly go sideways and put the team's life in danger.

The trailer for the next episode shows the Intelligence team uncovering the murder weapon, only to consequently find themselves in the middle of the biggest gang war to ever break out in the city. Will they be able to quell the chaos at the expense of their own lives, and will the reopened cold case finally be given its due justice?

Meanwhile, Voight (Jason Beghe) may not be giving Ruzek the warmest welcome when instead of taking him back into the team, the squad commander knocks him down to patrol duty. Will Ruzek have to work his way back to Voight's good graces, or will Voight be doing this for Ruzek's own good?

In other news, actress Squerciati has recently announced her pregnancy via her official Instagram account. As to whether or not this would be written into the series, Squerciati was quick to thwart this speculation through the photo's caption: "Don't be surprised to see Burgess holding a LOT of file folders in front of her stomach."

"Chicago P.D." season 4 episode 15 airs on Wednesday, Feb. 22 at 10 p.m. EST on NBC.