|Season 3, Episode 12|
"Let Him Die"
Detective Atwater from Chicago P.D. joins the search in the storage unit and agrees that all signs point to an arsonist's arsenal, but he still warns that arson remains difficult to prove. Curious about the newspaper clipping of Shay and its link to the storage locker, Severide and Dawson revisit the collapsed building where Shay died and, in an emotional moment, they both remember how and where Shay took her last breath. Severide notes that the burn patterns don't match his memory - they need to check the official file.
Back at 51, a major two-car crash shocks the squad when they discover Chaplain Orlovsky in the driver's seat, unconscious and bleeding. But in a controversial move, Casey makes the call to help the other car's injured driver first. Although the team saves both victims, Orlovsky remains unconscious for an extended period at the hospital, during which Casey questions his initial decision and attempts to locate a living relative in the event of Orlovsky's death... to no avail. Luckily, Orlovsky makes a full recovery, and as a show of appreciation, Casey and Herrmann enlist Herrmann's peewee hockey team to paint Orlovsky's apartment.
Meanwhile, both Brett and Mills turn down time off in response to their recent traumatic incident - and only Brett agrees to see a counselor. Later, they make a house call and find an obvious victim of domestic abuse in distress, but with her standoffish husband around, she refuses treatment. On a separate call at Chicago Med, Mills spots the same woman - now hospitalized - and in a rage he returns to the original apartment and assaults the husband, threatening to kill him if he hurts his wife again. The move frustrates Brett - not just because Mills' actions could have consequences, but also because he lied to her about why he needed to visit the husband.
Another visitor proves prickly when it appears that Boden's dad may stay longer than intended - and his continuous string of unsolicited child rearing advice takes a toll on Donna. She urges Boden to chat with his dad, but when he does, his dad's response stops him cold - he's got stage four cancer. Later, Boden holds back tears as he thanks his dad for coming to Chicago.
Severide's off-the-books investigation continues as he reaches out to a contact in the arson department. She manages to take secret photos of the original file on Shay's case, and after Dawson and Severide analyze every page, they identify several consistencies that suggest the burn patterns were manipulated using a trail of shredded paper. They again return to the original fire scene and scour for clues. At long last, Severide discovers the charred remnants of a slow-burning fuse.
Which means not only was Shay murdered, but whoever committed the murder remains at large.