In season 1 of Chicago P.D., it has been established from the very beginning that Lindsay shared a special relationship with Hank Voight, head of the Intelligence Unit.

Through Bunny, she has a half-brother, Teddy Courtney, who was taken by a pedophile ring at age 13 and was found by NYPD detectives ten years later working as a prostitute.

[4][5] Lindsay grew up on the street, and by the age of 14, she had already been arrested five times on charges including misdemeanor, simple battery, retail theft, solicitation, and unlawful possession of cannabis.

[7] After graduating from the police academy, she spent four years on the west side of Chicago as a patrol officer, which she said was all the education she needed.

[13] Lindsay's spiral downward begins with Nadia Decotis' death in the Law & Order: Special Victims Unit crossover episode "Daydream Believer".

She returns in the season 3 premiere after learning that Halstead's undercover operation had been compromised and that he was being held hostage and tortured by a drug kingpin wanted by the Chicago PD.

They share a close friendship, which has escalated to a more intimate relationship and cooled down at various times, due to Voight's vocal dislike for "in-house" romances.

When Lindsay was on the federal task force, she starts seeing Halstead after work as they no longer had to worry about breaking fraternization rules.

She leaves Chicago in "Fork in the Road" to join the FBI's New York Counter-terrorism Bureau in exchange for her mother's freedom after she is found in possession of pills that were stolen by her boyfriend and his associates.