Continuity mistake: The head of pediatrics is talking about Doug to Mark and Dr. Morgenstern and is holding his glasses in one hand. From one shot to another they flip right over in his hand, with no time for him to change them.
Continuity mistake: Carol's notary asks her for some water and she takes the cup in one hand and the jug in the other and pours. The next shot shows one hand still pouring and the other up on her papers. She had no time to put the cup down and move her hand.
Continuity mistake: Carol is signing papers for the notary and he is complaining about his job - he has one hand up on his large book and the other in his lap. The shot changes and his arm and hand are under the book, with no time to shift naturally.
Continuity mistake: Harper is talking to Mark about her night with Doug and her stethoscope is hidden in her collar and lapel on her right. As the shot changes and she turns, it is suddenly fully visible and the left side has moved much further up towards her neck.
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.