'Chicago Fire': Major Character Plans to Propose in Crossover, but There's a Heartbreaking Twist

One of Chicago Fire's most beloved couples was headed toward a happy ending, but the crossover event saw the relationship take a major step in the wrong direction. The NBC firefighter drama series kicked off the eventful three-hour installment that brought the three shows together to fight a flesh-eating bacteria killing people in Chicago. The episode also gave an status update on a longstanding relationship on the show, though it ended with a sad cliffhanger.

Spoilers ahead for Chicago Fire, Chicago P.D., Chicago Med crossover event: "Infection"

While the three-hour event revolved mostly around the doctors, firefighters and detectives working to stop the spread of a man-made infection claiming lives across the city, there was still room for some relationship drama at Firehouse 51.

Near the start of the eventful crossover, Cruz (Joe Minoso) gets a surprise visit from his girlfriend Chloe (Kristen Gutoskie) at the fire station. She asks him to go to the festival and Oktoberfest parade planned for downtown later that day, but Joe nervously tells her he has to work the event.

Cruz acts fidgety and nervous throughout their conversation, which raises a flag for Chloe and she asks him what is going on. The question just makes him act weirder, however, which Mouch (Christian Stolte) and Brett (Kara Killmer) can't help but notice as they are in the same room.

Later, Mouch and Brett notice him find Cruz nervously talking to himself in the kitchen and decide it's time to confront him about what's going on.

He tells them not to say anything, but reveals he is planning to planning to propose and has a very special night planned for the next day after shift. Brett and Mouch congratulate him on his decision and say she is the perfect match for him

The subject comes up again after the firehouse responds to a massive fire at a university, Chloe is waiting for Cruz and confronts him about making a reservation in the most expensive restaurant in Chicago. He says she deserves a special night out, but she seems to know what is going to happen.

Rather than celebrating the possible engagement, Chloe admits she's having second thoughts about their relationship. She thought about it a lot and things feel rushed between them, so she suggests they need to take time and think before making any steps forward.

Cruz says her decision makes no sense, but Chloe apologizes and drives away, leaving Cruz brokenhearted.

Will the couple make things work in the end? Chicago Fire airs Wednesdays at 9 p.m. ET on NBC.