S2, E14: Severide (Taylor Kinney) feels sidelined as he leaves Detective Lindsay (guest star Sophia Bush) and the Intelligence Unit to do their job and locate his sister Katie (guest star Brittany Curran). Shay (Lauren German) gets an unusual tip from Chicago Blackhawk players Brent Seabrook and Duncan Keith, who makes friends with Clarke (guest star Jeff Hephner) and stop by Molly's. Meanwhile, Casey (Jesse Spencer) learns more about his head injuries after another close call and Dawson (Monica Raymund) pushes hard to pass the physical test at the Academy.