Grabbing a cup of coffee, Severide runs into Heather and the kids at the local cafe. He's genuinely excited to see them, but Heather? Not so much. Kelly tells her he's been meaning to come by, but Heather stops him, fire in her eyes. She claims Andy would have never even been a firefighter had he not known Severide. The squad gets called in to take care of a small kitchen fire that they put out within seconds. When Severide spots Mills with one hand on the ladder, he's infuriated. "Men die when they relax!" he shouts, undeniably ticked off. He heads over to Leslie, who hands him another one of those mysterious medicine vials. The last one.
At the firehouse, the men are all getting excited for the annual firefighters' barbeque. When Severide hears the Dardens are going to be there, he tries to get out of it by picking up an extra shift, but the Chief's not having it. Herrmann, back from the hospital, limps into the firehouse, telling the guys he may never walk straight again. After distraught glances are exchanged, Herrmann hops up and does a little jig. He's only kidding, after all! The Chief introduces Nicki Kahler, who'll be helping with the payroll. Eyes widen as she steps in; she's stunning, all long limbs and mysterious smiles. The daughter of an old friend, the Chief expects everyone to treat her like she's their sister, but some tension is already felt between her and Severide.
A piercing alarm breaks up the fun as the squad's called in to a site where three men are trapped under a collapsed building foundation. Two of the men are badly injured but saved by the squad, while one older man, Peter, is trapped beneath a boulder. An over-eager Severide climbs down to where he is, though the structure is still wildly unstable. Peter's obviously in terrible pain, but he's talkative. He makes Severide promise to be completely honest with him about his condition. With a pause, Severide tells him that he's most likely bleeding internally, and it doesn't look good. After Dawson checks him out, it becomes clear that for any hope of survival, Peter will need his leg amputated.
While waiting for the trauma surgeon to arrive, Severide and Peter amicably converse, trying to lighten the circumstances. Peter advises Severide not to wait long to get married, and tells him about the love and light of his life, his wife Georgie. As the minutes pass, Peter begs Severide to take care of his leg: he wants to go home. Casey tells Severide they need to clear out, as the structure could give at any moment, but Severide demands a saw and keeps Peter talking. The trauma surgeon finally arrives, but Severide crawls out of the hole and tells them it's a recovery now. Walking away from the scene, he looks down at his black gloves, covered in blood.
Back at the firehouse, Herrmann and his family surprise Shay and Dawson with a homemade sign for saving their father's life. Severide looks on, distressed that he couldn't save Peter. The crew attends a white board meeting where they discuss the mistakes made during Darden's death in hopes of preventing such future tragedies. Severide can't stand to be in there and escapes to the bathroom stall, inserting the mysterious medicine into his arm. Later that day, Heather drives up to Casey's house to discuss the upcoming barbeque. It's a bit awkward, but they decide to go together. Shay and Dawson attend to a completely inebriated man causing trouble in an Irish bar. As they fix him up in the ambulance, Shay mentions the rumors circulating about Casey and Hallie's reported split. Dawson's eyes immediately light up at the news. Are there feelings there?
On the day of the barbeque, everyone's in casual civilian attire while Mills shows up in full uniform, still getting picked on by the guys. There are many prices to pay when you're a newbie and don't know any better. Casey, Dawson and Shay all sit at a table with their significant others, all getting to know one another. When Dawson tells the group that she's been taking med school classes, Hallie sweetly offers Dawson the chance to shadow her at the hospital for extra experience whenever she'd like. Dawson is touched by the gesture, but also secretly frustrated that the fiancee of a man she has feelings for is a genuinely nice person.
Heather Darden arrives with the boys, and Casey scoops them up immediately, making sure they feel comfortable playing with the other kids. Hallie watches, touched by how good Casey is with them. Nikki introduces herself to Severide over the beer cooler, making sure he knows she's interested. Meanwhile, Casey and Dawson strike up conversation, Casey asking Dawson about her date. Hallie watches from across the field, concern wavering across her face. She can tell that there may be something between them, even if it's unaddressed. After the barbeque, Nicki shows up at Severide's apartment with his jacket in hand. She returns it to him and swoops in for a kiss, no problem being forward. Severide's amused, but tells her now's not a good time because a Cubs game is on. Nicki saunters down the hall, disappointed but not defeated.
Back at Severide and Shay's apartment, Shay brings up Heather Darden, but Severide doesn't want to talk about her. He's been making mysterious phone calls these past few days, always leaving voice mails asking the anonymous person to call back. Another day, another emergency. The squad's called in for a rescue involving a window washer's cart blowing in high winds 40 floors up, part of which crashed onto a parked car, trapping two young women. One of them was instantly killed, while the other, Julie, is wedged into her seat. The firefighters are working against time, as pieces of the cart are still continuing to crash down onto the sidewalk. As Severide works to saw open the door of the car, the cart above swings with the wind, held up by a single rope.
The crew is able to get Julie out in time. Severide finally gets a call back, and promises the caller he'll meet them at the agreed-upon time. Later that day Casey shows up at Hallie's work, asking her to start fresh. He wants to put their issues about children and work and life aside; all he wants is to be with her. He slips the engagement ring back on her finger, and they embrace, hearts full. At night, they meet the crew at a bar, where everyone's relaxed and sharing rounds of shots. For a second, Dawson's eyes linger on Casey's arm around Hallie. Hallie asks Dawson if she's thought more about doing rounds with her at the hospital, assuring her Dawson has more experience than half of those Ivy League clowns trying to be doctors.
Instead of being at the bar, Severide is walking up the steps to a suburban house on a dimly lit street. All of a sudden we see a video of Peter, the deceased man from the building accident. It's being played on Severide's phone, a video addressed to Georgie. A goodbye video. The camera pans out and we see Georgie holding the phone watching the video, Severide seated on the couch right beside her. In the video, Peter tells Georgie that Severide is the kind of son they always wanted to have, but never did. Geogie looks over at him with tears streaming down her face and Severide returns her glance, his dark eyes red-rimmed. As the video ends, Georgie embraces him, thankful for having heard her love's final words. The camera strays on Severide's face, his eyes bearing the weight of the world, all the things he cannot say out loud.