No. in series No. in season Title Directed by Written by Original air date Production code U.S. viewers (millions) 114 "Leave It to Weaver '' Jonathan Kaplan Lydia Woodward September 30, 1999 (1999 - 09 - 30) 225451 31.53 Greene and Weaver agree to go out on a limb to oppose Romano 's appointment as chief of staff. However, soon Greene finds he is out there and alone, while Weaver reaps immediate benefits for her treachery. Plus: Luka Kovač is an able, yet untrusted, physician from Croatia arrives at the ER for his first day of work; Carter 's interested in a romance with his cousin 's ex-wife; and Hathaway adjusts to being pregnant alone. NOTE: First Appearances of Dr. Luka Kovač and Dr. Cleo Finch. 115 "Last Rites '' Félix Enríquez Alcalá Jack Orman October 7, 1999 (1999 - 10 - 07) 225452 28.20 Who 's the boss? Weaver may be head of the ER, but Greene has his own ideas about how to handle situations and after his mother 's death the two of them have their worst conflict on the job yet. Boulet says "yes '' to Reggie, and Corday accepts Romano 's surprise job offer. A brash new resident arrives and manages to annoy just about everyone. Carla confronts Benton about not allowing her to leave the country with their son. Carter and Elaine 's relationship continues. NOTE: First Appearance of Dr. Dave Malucci. 116 "Greene with Envy '' Peter Markle Patrick Harbinson October 14, 1999 (1999 - 10 - 14) 225453 30.45 Newly appointed attending physician Gabriel Lawrence is savvy, personable and, in Greene 's jealous opinion, unsuitable for County. Jeanie and Reggie marry, but not under the circumstances they expected. Romano makes Corday show a rude reporter around the ER, where she witnesses a shootout. Carter tries to be supportive as Elaine undergoes her mastectomy. Greene and Corday spend their first night together. 117 "Sins of the Fathers '' Ken Kwapis Doug Palau October 21, 1999 (1999 - 10 - 21) 225454 N / A Greene deals with the fallout from his dad 's car accident. Lawrence suspects a teen 's suicide attempt is the fallout from father - son strife, but he is wrong. Finch misdiagnoses a little girl 's behavior before an iron overdose has the staff battling to save the little girl although they are unsuccessful. Hathaway tries to help a pregnant woman get a job at the hospital, and Dr. Dave Malucci is a jerk again. Carter makes plans to meet with Elaine. 118 5 "Truth & Consequences '' Steve De Jarnatt R. Scott Gemmill November 4, 1999 (1999 - 11 - 04) 225455 N / A A high school science experiment / prank gone - wrong lands students and teachers in the ER - and the stress of multiple emergencies pushes Lawrence over the edge. Greene defends a patient from a violent parent and ends up being castigated for it. Lucy helps counsel one of the injured students. Hathaway learns the pregnant woman she wanted to help is using drugs. Elaine tells Carter that she intends to go to Europe for a couple of months asking him not to contact her. 119 6 "The Peace of Wild Things '' Richard Thorpe John Wells November 11, 1999 (1999 - 11 - 11) 225456 N / A Boulet resigns to be a full - time mother. An elderly woman bids farewell to her dying husband, and Lawrence admits he is in the early stages of Alzheimer 's, and that his distinguished career is over. Hathaway takes action regarding the pregnant drug - addict case. An explosion rocks the ER, and Benton tells Carla why he is fighting to stay in his son 's life. NOTE: Final Regular Appearance of Physician Assistant Jeanie Boulet. 120 7 "Humpty Dumpty '' Jonathan Kaplan Neal Baer November 18, 1999 (1999 - 11 - 18) 225457 28.77 Lawrence departs (but not before saving a life), and Kovač comes aboard full time after earning Weaver 's respect. Corday discovers her new trauma patient is a rapist and takes extreme measures to find his latest victim. Hathaway and the formerly pregnant drug - using woman have a confrontation. Carter angles for more responsibility inside the ER. Greene 's father was due to fly into Chicago but shows up hours after his scheduled arrival time. And the Bright Star Gospel Choir is rushed to the ER. 121 8 "Great Expectations '' Christopher Misiano Jack Orman November 25, 1999 (1999 - 11 - 25) 225458 30.80 It is Thanksgiving, and Hathaway has two more reasons to give thanks after overcoming complications and delivering twins Tess and Kate. Greene 's family celebration comes with its own complications. Malucci stuns the staff by actually having a valid idea to treat a patient that works. NOTE: First Appearance of Nurse Abby Lockhart. 122 9 "How the Finch Stole Christmas '' Fred Einesman Linda Gase December 16, 1999 (1999 - 12 - 16) 225459 29.10 Lucy risks Romano 's wrath (and her career) to arrange a heart operation for a patient. Carter gives gifts to inner city kids in exchange for their guns. Finch uses her authority to put a teen binge drinker into rehab. Benton and Carla 's custody battle comes to an abrupt end that works out in his favor. Weaver befriends a group of Santas and works on County 's Y2K preparation. 123 10 "Family Matters '' Anthony Edwards Patrick Harbinson January 6, 2000 (2000 - 01 - 06) 225460 28.69 Deb Chen returns to the ER as Jing - Mei Chen and immediately shows off her great photographic memory to Carter 's annoyance. Kovač 's strong sense of family involves him in the fate of brothers facing separation. Greene invites his dad to reside with him in Chicago. Malucci fixes Weaver 's car and learns a young patient has a fatal disease. Goofball students arrive in the ER to do a scavenger hunt. Benton does not agree with Cleo 's approach to an overstressed young high school athlete. NOTE: Dr. Jing - Mei "Deb '' Chen returns to the show after having been a recurring guest star in Season 1. 124 11 "The Domino Heart '' Lesli Linka Glatter Joe Sachs January 13, 2000 (2000 - 01 - 13) 225461 N / A A precious donor heart becomes available when a patient who recently received it dies, devastating Lucy. Malucci gathers evidence to shut down a backroom clinic. Carter and Chen disagree on when to follow rules and when to break them. Greene learns a man is being abused by his boyfriend. 125 12 "Abby Road '' Richard Thorpe R. Scott Gemmill February 3, 2000 (2000 - 02 - 03) 225462 N / A Abby Lockhart, the part - time OB nurse who cared for Hathaway during "Great Expectations '', reports to the ER for her third - year med - student rotation. Hathaway has a hunch that a young patient 's health problems come from his mother. Carter and Cleo try to help a sick boy and the unpopular student he fought with. Weaver leaves the ER due to the flu, while Malucci works in spite of it and Benton angles Romano 's illness into some help for a young girl who was mauled by a dog. 126 13 "Be Still My Heart '' Laura Innes Lydia Woodward February 10, 2000 (2000 - 02 - 10) 225463 31.33 It 's a tense Valentine 's Day in the ER with the case including an operation on Romano 's dog and a car crash that leaves two children orphaned while a patient, Paul Sobriki (David Krumholtz) complaining of headaches arrives in to be treated and his symptoms has Lucy suspecting that the patient has schizophrenia but her warnings to Carter go ignored which later results in disastrous consequences for the entire ER. The episode then ends in a cliffhanger as both Carter and Lucy lie on the ground, bleeding heavily, Sobriki having attacked and stabbed both of them while suffering a psychotic episode. 127 14 "All in the Family '' Jonathan Kaplan Jack Orman February 17, 2000 (2000 - 02 - 17) 225464 39.38 The ER 's Valentine Day party continues as Weaver arrives for her shift. Weaver later stumbles into an Exam Room and discovers both Carter and Lucy on the floor of patient Paul Sobriki 's room, both doctors unconscious and bleeding heavily after Sobriki attacked and stabbed them while suffering a psychotic episode. The celebrations then abruptly ends as the ER staff jump into action and find themselves battling against the clock and ever - decreasing odds to save their grievously wounded colleagues, both of whom are hovering between life and death. As Carter and Lucy are brought up to surgery, the ER staff attempt to come to terms with what has happened. Luka tries with little success to convince Sobriki 's wife, Samantha, that her husband is gravely ill. In the OR, it 's chaos as Benton and Anspaugh fight to save Carter while in another operating room, Corday and Romano battle to save Lucy. Meanwhile Cleo finds herself being forced into a surgical role when it becomes obvious that Benton will not leave Carter. Corday and Romano desperately try to save Lucy 's life, but she succumbs to her injuries and dies, leaving the entire ER team grief - stricken and devastated. NOTE: Final Appearance of Medical Student Lucy Knight. 128 15 "Be Patient '' Ken Kwapis Sandy Kroopf February 24, 2000 (2000 - 02 - 24) 225465 31.31 Carter struggles with rehab and knowledge of Lucy 's fate, a child is injured in a hit and run in front of Kovač (and the driver later turns up in the ER), and a teen has cervical cancer after becoming infected with HPV. Even a happy event, a romance between Isabelle and David Greene, turns sad when Greene learns his dad is terminally ill. 129 16 "Under Control '' Christopher Misiano Neal Baer & Joe Sachs March 23, 2000 (2000 - 03 - 23) 225466 27.19 "We can handle this. '' This, it turns out, involves a Gila monster, toxic breast milk, a deadly error and much more as Greene oversees a particularly hectic shift. Carter, despite his pain, returns to work. Chen is attracted to a very handsome male nurse. 130 17 "Viable Options '' Marita Grabiak Patrick Harbinson April 6, 2000 (2000 - 04 - 06) 225467 27.50 Kovač and Corday must select a recipient while a donor kidney is still viable. Weaver defies Romano on treating a poorly - insured patient and is suspended. Benton 's careless penmanship results in a patient taking the wrong drug, and he blames Finch when the patient ends up in the ER and later in the operating room having suffered a heart attack. Chen wants to tell the daughter of a patient about her father 's diagnosis of Huntington 's Disease but Greene puts the brakes on that. Greene has his own conflict with both his father and Corday over David 's desire to check into a hospice care center. 131 18 "Match Made in Heaven '' Jonathan Kaplan R. Scott Gemmill April 13, 2000 (2000 - 04 - 13) 225468 26.01 A notice of Lucy 's acceptance into psych residency deepens Carter 's remorse. Greene cares for his dad. Hathaway has news from Ross. An overwhelmed mother tries to induce a miscarriage before getting abortion help from Abby. 132 19 "The Fastest Year '' Richard Thorpe Lydia Woodward April 27, 2000 (2000 - 04 - 27) 225469 27.38 Memories. After his father reminisces about his Navy days, Greene takes him on a final boat ride on Lake Michigan. Meanwhile, Carter is haunted by terrifying thoughts of the attack that almost killed him. Kovač helps Hathaway buy a used car, before describing what happened to his family in Vukovar. Abby goes too far when trying to arrange for a bone marrow transplant. 133 20 "Loose Ends '' Kevin Hooks Neal Baer May 4, 2000 (2000 - 05 - 04) 225470 26.65 Malucci treats a little girl who was molested by her father. Hathaway 's birthday is anything but happy. Benton and Kovač clash over follow - up care. Carter seems reinvigorated but also ignores the orders of his supervisors. Greene and his dad manage to express their love just before David passes away. 134 21 "Such Sweet Sorrow '' John Wells John Wells May 11, 2000 (2000 - 05 - 11) 225471 32.67 Do open arms still await her in Seattle? Touched by a family tragedy at the ER, Hathaway realizes she must see Ross. Chen notices Carter 's increasing unreliability and mood swings. Abby is supervised by Malucci on a case that leads Corday to tell him that no one at County thinks he is any good at his job. NOTE 1: Final Regular Appearance of Nurse Manager Carol Hathaway. NOTE 2: George Clooney makes an unexpected uncredited cameo as Dr. Doug Ross in this episode. 135 22 "May Day '' Jonathan Kaplan Jack Orman May 18, 2000 (2000 - 05 - 18) 225472 34.59 Kovač and Benton rush to the scene of a school shooting, leading to a confrontation over who is the most critical patient: the shooter or one of his victims. The team plan an intervention when Carter 's addiction forces them to act. Kovač 's sense of right and wrong influences his care for his patients.
er episode where carter and lucy get stabbed
Be Still My Heart