Boden narrates the previously on section about how the job brings people together and comes at great personal cost.<P>
It’s not smoke, but it’s steam, as Severide returns and joins his wife in the shower, leading to a very racy scene for this series.<P>
Someone named Chippy rips Mouch’s name off of his locker, and Herrmann objects furiously. Seconds later, Mouch returns. He’s been in rehab for six months, has seen them frequently Mollys, but it’s his first day back at work.<P>
Firehouse 17 is sharing space with 51 while their own house is in disorder.<P>
Gallo is moving to Detroit to be with his newly discovered extended family.<P>
Before a call, Sylvie gets her engagement ring caught on her locker. Her locker contains photos of her entire family, including Casey, the boys, and Julia.<P>
The whole house is called to a horrific fire on a delivery truck. A man is trapped inside. On fire, he jumps free when the door is opened, but he’s quite charred.<P>
The burning truck threatens a bridge, so the team springs into action.<P>
Purple smoke indicates something inside that truck wasn’t right. Stella hopes the driver can shed light on it, but Kelly points out that he was in there a long time, so it’s a longshot.<P>
Sylvie’s wedding is a month and a half away. Right after, Sylvie is taking Julia and moving to Oregon.<P>
Kidd wants to keep Ritter on Truck, but Herrmann isn’t happy about it. Cruz says he was caught between two lieutenants before, and it was awful. His tactic was to let his lieutenants decide for him.<P>
The delivery truck driver died during surgery. <P>
Severide is trying to get the smell of the purple smoke out of his coat, but he can’t get the job doe. One of the Firehouse 17 guys realizes the odor reminds him about the fire at his own house. Is there a connection?<P>
They thought a box of cleaning supplies might have been the culprit, but now they’re not so sure.<P>
When Kelly wants to look into it, Kidd gets concerned that arson might be his crack. She’s still reeling from the fact she had to drag him home, and it’s taken six months to rebuild some semblance of trust. He promises her they’re in it together, and this won’t be like the last time.<P>
Severide experiments with chemicals in the parking lot while discussing it with Cruz and Carver. He finds the deadly combination quickly. If these are deliberately set fires, someone is trying to kill.<P>
As Mouch and Boden catch up, Mouch is the voice of viewers as he notes that with Gallo gone and Brett leaving, it’s just not the same anymore. Kylie interrupts. She’s in uniform. She’s charting her own path at another firehouse. She just wanted to see Mouch back on the job.<P>
Ritter and Violet are making lasagna, and without Gallo’s sauce, they’re worried. Herrmann remembers bringing Ritter to Engine. Fond memories, he says, as Kidd calls foul. Ritter needs space to make an unbiased choice between Truck and Engine.<P>
When Carver asks about a plus one for Brett’s wedding, she offers up Violet. From their nitpicking, it seems like Carver and Violet are going to act on the suggestions that were alight last season.<P>
Severide visits Van Meter about the investigation. Van Meter joins Severide to see the remains of the delivery truck for more insight into the fire.<P>
Van Meter notes that Kelly hasn’t been around OFI for a while and that he heard from Douglas Smith from the ATF Arson Program that Kelly took his name off the National Investigator’s List. It’s a prestigious group, and Van Meter hopes Kelly doesn’t waste a once-in-a-lifetime opportunity.<P>
Kelly finds a rat trap that indicates an incendiary device. Someone seems to be targeting firefighters.<P>
Mouch is like, damn. I almost got killed on the job and spent six months in rehab to return to someone gunning for firefighters.<P>
Kidd gathers Truck for drills. After they race with some ladders, Gallo drops by for his goodbye scene.<P>
Gallo is so excited for the next chapter in his life. Replacing the family at 51 with his actual family will hurt, but everyone is so happy for him.<P>
The three amigos say a tearful goodbye before Riolet and Vitter are called to an emergency.<P>
The call is to a rollover accident filled with blood but missing a victim. They can’t imagine how someone could survive that accident, but alcohol seems to have kept him alive. Practically scalped and in bad shape, he’s ready to just go on home. <P>
Carver compliments Violet after the rescue with a glint in his eye.<P>
Everyone at the firehouse is on edge. Every snap of the radio frays their nerves with the expectation another firehouse has been targeted.<P>
Severide is at Firehouse 105, trying to get an idea about the fires. It’s there that he realizes the arsonist is targeting Firehouse 17 in particular. Everyone is spread around the city after 17’s fire, and the arsonist is following them.<P>
Herrmann spots the guy he saw at the delivery truck explosion, and Boden is in hot pursuit, dragging that bastard right out of his car. Meanwhile, Herrmann finds and exposes of the box, but he’s pretty close to it as it explodes.<P>
The culprit is Alan John Webber. He was a washout rookie at 17 over eight years ago and has been spiraling ever since. He blames the firehouse for his hard times. Instead of killing a firefighter, he killed someone merely caught in the crossfire.<P>
Herrmann’s heroism drives Kidd to send Ritter back to Engine. It’s hard to tell how Ritter actually feels about it.<P>
Violet tells Brett how much she’ll miss her. She doesn’t want to hold it all in like she did with Gallo. Every day, she’s going to tell Sylvie exactly how much she means to her.<P>
Ritter tells Herrmann he’s coming back to the rig. Truth is that he’s an engine man at heart. Ritter worries about Herrmann getting knocked back by the explosion, but Herrmann says he’s fine.<P>
Stella tells Kelly she’s proud of him, making him happy. He admits it felt good to be on the arson beat again. He wants to keep it in his life without pushing the two of them apart. She wants to be able to say hell yeah, go for it, but it still hurts. His time away left deep scars, and it will take time for that to go away.<P>