Chicago P.d. - Season 4 -

In a devastating multi-episode arc, Alvin Olinsky (Elias Koteas) loses his daughter, Lexi, in a warehouse fire, pushing him to a grief-stricken breaking point.

The season begins with Commander Emma Crowley (Barbara Eve Harris) investigating Voight and Lindsay for the murder of Justin Voight’s killer, a dark secret that strains their relationship. Chicago P.D. - Season 4

A cross-show romance developed between Antonio Dawson and Chicago Fire 's Sylvie Brett. In a devastating multi-episode arc, Alvin Olinsky (Elias

Season 4 marked the end of an era for two of the show's original leads and introduced a future mainstay: In a devastating multi-episode arc

A crossover with Chicago Fire (Season 5, Ep. 9) where Kelly Severide is suspected of vehicular manslaughter.