Shay and Dawson visit frequent 911 caller Darryl to help him with his insulin injection. They're both annoyed at his neediness - he's clearly infatuated with Shay - but stop short when he pulls a gun and points it at himself. Despite their desperate pleas, Darryl squeezes the trigger - his blood splattering their clothes.
Although his suicide affects both women, Shay becomes despondent and withdraws - an issue compounded when Dawson pulls rank during an argument and the two declare their friendship over. Shay takes comfort in booze and bonds with her new roommate Otis - a respite that only lasts until her laughter devolves into sobs. Otis agrees to keep her breakdown a secret.
Meanwhile, Chief Boden visits the CFD Deputy Director and asks him to get McLeod to ease off Station 51; she's overstepped her boundaries. On cue, McLeod surprises Boden at his office to clarify that she's only accountable to the state - not the city, not the CFD and certainly not to Boden.
When Boden escorts McLeod out, Benny happens to notice, spurring his own visitation to McLeod, where he expresses his support for the firehouse... and disdain for Boden. With that shock under wraps, another lets loose: Mills spends enough quality time with Clarke to discover he refused McLeod's directive. So who's the stationhouse rat? After a shady encounter with Spellman, Mills calls him out - and Spellman slinks away, clearly hiding the truth.
At a meet and greet spearheaded by Isabella, Mouch rubs shoulders with voters, until a familiar foe crashes the party: Hadley. He accuses Mouch of being a terrible union rep and ruins the event. Outside, Severide tails Hadley back to the house and plants a phone inside his car. He tracks the phone and Hadley's car to yet another dangerous building - and this one's already in flames.
Severide calls in 51, and they rush inside looking for Hadley, a tough job given all the smoke. Hadley instead finds Severide and shows off enough explosives to take out the whole city block. The two men wrestle, and suddenly fire lights up across Hadley's body. He falls unconscious as they extinguish the flames...
Still stinging from the suicide and her fallout with Shay, Dawson watches the Darden boys on the playground when she's interrupted - for the umpteenth time - by a call from Jay. She instructs him to leave her alone, then hears a nearby scream - from Griffin, on the ground after a nasty fall.
At the hospital, doctors reveal he suffered a cracked rib, and Dawson confesses her guilt to Casey. He tells her not to worry and later learns Griffin's more hurt by his incarcerated mom than the injury. The pair bonds as Griffin requests Casey stay with him until he falls asleep.
But the biggest news occurs when Herrmann ropes in Antonio to help smooth out Jay and Dawson's affair, hoping the detective can create a little distance for his sister. Turns out it was a brilliant move because Antonio relays some highly confidential information to Dawson - Jay's not working for the thugs. He's working undercover for the CPD.
The fallout from a deadly routine call causes a rift between Shay and Dawson. Meanwhile, Severide goes stealth in his pursuit of Hadley.