Sean Roman has been absent from the Chicago P.D.world for four years, but in the latest crossover with Chicago Fire, the former patrol officer returns to the Windy City -- not to rekindle an old flame, but because his sister is in deep, deep trouble.
In Wednesday's two-hour event, a bearded Roman (Brian Geraghty) arrives in Chicago seeking help from his old colleagues. But his first stop isn't the police station, as one would assume. It's Firehouse 51.
In ET's exclusive sneak peek from part 1 of the crossover on Fire, Roman's unannounced appearance at the firehouse surprises Sylvie Brett (Kara Killmer), who welcomes Roman with open arms. "Oh my god, Sean!" Brett exclaims, puling Roman into a hug. "How long has it been?"
"Four years," Roman updates Brett, who is joined by Emily Foster (Annie Ilonzeh) midway through the conversation.
Roman and Brett continue with their small talk, comparing the unforgiving Chicago winters to the milder, sunnier San Diego climate he's called home the past four years, before Foster introduces herself and learns a little bit more about who he is.
"I get to wear shorts year-round now," Roman jokes, after filling Foster in on that injury that "sidelined" him for good, as he got nostalgic over what once was his home. "But I do miss Chicago."
But before Brett could bring him in to get reacquainted with everyone at 51, Roman reveals the real reason he's in town -- and it's far more dire than Brett and Foster could even contemplate. A missing sister, a dead best friend, Roman needs all the help he can get to get answers to what happened. Watch ET's exclusive sneak peek above.
Geraghty left P.D. at the end of season three when Roman opted to relocate to Southern California rather than resign himself to a desk job after having his career as a field officer abruptly cut short following a serious injury. He unsuccessfully tried to persuade his ex-flame, Kim Burgess (Marina Squerciati), to go with him.