At Casey's house, Heather Darden's boys refuse to get ready for school - that is, until Dawson shows up. They respond to her immediately and Casey notices - could this be the connection Dawson's pining for? It seems that way, until she privately admits to Shay that she wants to date outside of Firehouse 51. Turns out Jay - one of the only regulars at Molly's - fits the bill. He's cute, charming and definitely not a firefighter. She asks him to a Scotch tasting and he agrees.
Meanwhile, Renee returns home early, brimming with excitement about the baby. Severide responds with a serious question - is she certain the baby's his? She slaps him across the face and storms out.
Still reeling from the altercation, Severide seeks out his dad, Benny, to follow up on the string of fires from last week. Benny agrees to work his connections in Arson, but warns that Severide might be wrong to think it's a criminal with a vendetta. On his own, Severide checks a map of all the fires and makes a startling determination - each one is on the dangerous buildings list. A list to which only a firefighter would have access...
Back at the station, Hermann preps Mouch for his first town hall meeting as a candidate for Union President. Mouch nails the rehearsals using Herrmann-approved key cards and the pair feels confident about his chances. But when Mouch attends the town hall, nerves and pressure overwhelm him and he loses the room.
Another shaky start receives a rough blow when Antonio relays the latest news from Heather Darden's case - her friend died and now Heather's looking at manslaughter charges. Casey remains optimistic until he hears straight from Heather - she accepted a plea deal and will be in jail for 15 months. She needs his temporary role as Griffin and Ben's caretaker to be more permanent. With this in mind, Casey levels with the boys about their mother and tells them to stay strong. The whole firehouse will be their family.
At home, Severide finds Renee in the midst of packing. A test proved he was right; the baby's not his. She'd convinced herself otherwise, eager to restart a relationship with Severide. They share a bittersweet moment as she leaves - Severide so close to becoming a father, to starting a family. Shay consoles him at the station and offers up her new three-bedroom place. They'll need a roommate, but they'll be okay.
An alarm interrupts and sends everyone out to a familiar place - the Mills' restaurant, consumed in flames. Shocked and infuriated, Mills ignores orders from Boden and rushes inside. His mother panics and the squad fears the worst until he returns with two saved items: his father's medals and an apparatus identical to the ones found at the other arsons. Someone's targeting the whole station.
The arsonist's not the only one, either. Gail McLeod, the emotionless consultant, shows up to the station unannounced, trumpeting 51's latest violation - an unauthorized tour for a child. The squad admits to giving Ben a ride on the ladder, but how would McLeod know about that? Everyone agrees - there must be a snitch in the house. And Mills and Herrmann both think it's the new guy, Clarke.
With the restaurant fire heavy on his mind, Severide thinks he and Mills share a common enemy - their old colleague at Firehouse 51, Hadley. He tracks down the embattled fireman at a bar and asks him point-blank if he's starting the fires. Hadley eggs him on: "You think I'm setting fires? Well, then I guess you better prove it." Severide grits his teeth - oh, he will!
That night, Dawson opens up Molly's so she and Jay can share a nightcap. While she dips into the back for some top-shelf booze, Jay steals her keys and sneaks a peek at the register. He returns the keys - and his charming smile - before she gets back, and Dawson's none the wiser. Is Jay really as nice as he seems?
Casey struggles to manage Heather Darden's boys. Meanwhile, Severide goes on the offensive in pursuit of the arsonist.