Continuity mistake: When Malik finds Carter's family noted amongst the richest in Chicago, he says that Carter's father is named 'Roland'. However, in later episodes, Carter's father's name is given as John Truman Carter, Jr.
Continuity mistake: During the opening credits, when they are working on an unconscious patient, his belt is undone and his fly is down. A couple of shots later, the fly is up and the belt buckled, even no one touched them in between.
Continuity mistake: Susan comes home carrying bags of groceries. When she first sees Chloe sitting at the door, a box of Kix cereal is on the side of the bag next to her body, but as she says "Chloe", the box is on the other side of the bag, away from her.
Answer: A man named Paul Sobriki comes into the ER in the season 6 episode 13 " All in the Family." He is complaining of headaches, Carter and Lucy decide to rule out meningitis and do a lumber puncture. Paul struggles during the procedure and believes that both doctors are stabbing him. Lucy, who is interested in Psych thinks something is wrong with their patient mentally, but Carter is dismissive of her. She gets cross with his attitude and she calls the psych department anyway to have a look at him. Later on and near the closing 20 minutes or so of the episode, all the staff start playing loud music and get a cake which appears to be blue lol, together to party as it's Valentines Day, Carter returns from somewhere and asks where Lucy is. He goes to check one of the rooms for her and Paul Sobriki comes up behind him in the dark and stabs him twice in the lower back, he collapses and as he falls unconscious he sees Lucy on the ground also. In the next episode, Be Still My Heart (ep 14), Dr Weaver discovers them and all of the staff work to try and save them, whilst Carter survives. Lucy's wounds are fatal and suffers a pulmonary embolism as Corday and Romano try to save her. Carter is grief stricken and feels guilty about the way he treated her, he becomes addicted to painkillers and Benton, Greene all help him and book him into rehab.