Sylvie Brett (Kara Killmer) becomes the target of a dangerous killer in the upcoming episode of the NBC series "Chicago Fire."

In "On the Warpath," Spoilers Guide reports that the paramedic will be responding to an emergency call involving a man with a leg wound. While trying to stop the patient from bleeding to death, Brett's situation will take a turn for the worse when an armed person comes and shoots the poor fellow. The culprit then goes ahead and threatens Brett that he will find and kill her if she tells the police what happened.

The promo shows the paramedic kneeling while treating the victim when a man wearing a hooded jacket approaches and shoots. He demands that Brett give him her identification card. When she eventually returns to headquarters, Brett's friends cannot help but notice how weird she is acting. The scene cuts to her getting a call from the killer where he tells her that the police will not be able to protect her forever.

The synopsis reveals that Brett will ask the help of Antonio Dawson (guest star Jon Seda) from "Chicago PD." Although she promised the shooter that she would not approach the police, Brett gets the courage to call the officer and tell him her plight. This angers the killer and makes him go after the paramedic. He has her address and important details on her ID. Stalking her will not be a problem. Will Dawson be able to help her out?

Meanwhile, Firehouse 51 will have a tough time responding to an emergency. A restaurant is on fire and there are a bunch of people trapped inside. Out of all the places to run to, they sought refuge inside a vault. Will the firefighters manage to get them out in time before they run out of breathable air or will the fire make sure no other soul gets out alive?

"Chicago Fire" season 4 episode 18 will air on Tuesday, April 5 at 10 p.m. EDT on NBC.