Detective Erin Lindsay’s (Sophia Bush) life is about to be turned upside down. When NBC series “Chicago P.D.” returns after the holidays in 2017, she is going to meet none other than her estranged father.

Lindsay will come face-to-face with her absentee father Jimmy (Tony Crane), TVLine reported. The meeting takes an unexpected turn when she learns that her father wasn’t in jail. Her mother had told her that her dad was behind bars all this time, but he wasn’t. He has been out of prison for the last ten years and during this time, he got married and fathered two boys. Jimmy tells her that this is the reason he never reached out to her.

However, Jimmy wants to get to know his daughter now. He wants to be a part of her life. Will she allow him to get to know her? And how does she feel about him abandoning her?

Well, “Chicago P.D.” fans will only know the answers to these questions on Jan. 4 when they meet Lindsay’s father.

However, before being introduced to the detective’s father, Lindsay will meet firefighter and “Chicago Fire” character Kelly Severide (Taylor Kinney). The meeting is a little awkward since they share a history. The ex-lovers bump into each other at a restaurant in Chicago, according to Entertainment Tonight. They make small talk before agreeing to go on a double date. Lindsay will bring her boyfriend Jay Halstead (Jesse Lee Soffer) and he will bring his girlfriend Stella (Miranda Rae Mayo) to the double date.

However, Severide will be in big trouble in the crossover episode between “Chicago Fire” and “Chicago P.D.” He will be charged with vehicular manslaughter in a hit and run case. Severide will need all the help he can get – including Lindsay’s – if he wants to prove his innocence.

“Chicago P.D.” Season 4 returns with a crossover episode with “Chicago Fire” on Tuesday, Jan. 3 at 10 p.m. EST on NBC. Then, on Wednesday, Jan. 4, “Chicago P.D.” airs another episode which introduces Lindsay’s father.