During a call, a nasty blow to the head brings Casey unimaginable pain.
He suffers from vision blurriness and short-term memory loss.
Having suffered a prior head injury, Casey worries that this injury could exacerbate the trauma to a debilitating level.
His sister Christy also comes to town to see what their late uncle Jake has left them.
Jake leaves them a watch worth $80,000, but Casey decides not to sell it.
Jake was given the watch by his late wife, and Casey didn't feel right selling it.
Mouch, Gallo, Ritter, and Mackey report for technical rescue awareness training at Firehouse 33.
During the training, Mouch doesn't follow the chief's instructions and shows off to the younger firefighters.
He doesn't get his certification and Boden yells at Mouch until Mouch explains that he liked feeling like the hero.
Boden then steps in to get Mouch his certification, telling Mouch he's always been a hero.
Mackey gets offered a job as a paramedic at 33, and after thinking it over, she decides to take the position.
She leaves 51 on good terms, and Gallo's ex Violet appears to be taking the open paramedic position.
Kidd orders a package for the apartment, and Severide worries what it might be.