Danny started the series as a patrol officer who aspires to become a detective. She has an on-again, off-again sexual relationship with Vic Mackey, and a complicated history with Dutch Wagenbach. Captain David Aceveda trusts her, helping her get reinstated after she is fired and arranging for her to be reassigned to Julien Lowe. Sofer becomes a mentor for Lowe, though the two don't see eye to eye on several personal issues and aspects of police work. She is forced to kill an Arab man, and the repercussions haunt her through several episodes as she is continually harassed. In season 5, she is assigned to desk duty as a result of her pregnancy. The identity of the father is unknown and is the subject of an office pool among her co-workers. Even though she is driven to the hospital by Julien, in her hospital bed after giving birth, Vic asks if Danny will tell the baby who the father was and she tells Vic that she will let the baby know, "when he's old enough," implying that Vic is indeed Lee's father. In Season 6, Captain Claudette Wyms promotes Danny to the rank of Sergeant, however, since open sergeants positions were filling rapidly, Danny was told she would have to end her maternity leave immediately in order to get a guaranteed full time position.
Danny is partnered up with Tina Hanlon and the two clash frequently as Danny feels that Tina is too inexperienced to be relied upon while Tina feels that Danny doesn't respect her or her skills. Things escalate when both women fix their eye on Kevin Hiatt, though Danny later admits that it was only to see if she could still "get her girl on." Later on, after hearing a confession, Danny consoles Dutch in the locker room and the pair share a kiss.