'Chicago Fire': Casey's Promotion Causes Friction With Severide (Exclusive Video)

Chicago Fire S04E01 Still - H 2015
Elizabeth Morris/NBC

Chicago Fire S04E01 Still - H 2015

There's serious tension in the air at Firehouse 51.

The most recent episode of Chicago Fire saw Casey (Jesse Spencer) promoted to captain, which means he now outranks Severide (Taylor Kinney), a lieutenant, for the first time. 

And it doesn't take for that change to cause major friction between the two, as seen in The Hollywood Reporter's exclusive video from Thursday's episode.

In it, the two clash over how best to try to save a man caught in heavy electrical wiring after falling off the side of a building. Not only do the two get in each other's face, but they also put the rest of the team, like Mouch (Christian Stolte) and Cruz (Joe Minoso) in the middle of their dispute.

It won't take long for their raised voices to remind loyal viewers of their intense season-one rivalry. Yikes!

So who comes out on top? Check out the exclusive video to find out.

Chicago Fire airs Thursdays at 10 p.m. on NBC.