Carter returns from Africa full of surprises including a new love, Makemba ("Kem"). Pratt accidentally breaks a patient's neck while doing an unsupervised intubation. A whole nursing shift cannot go home until they find one missing Valium.

Abby and Neela are assigned to a month-long rotation in the neonatal intensive care unit where they experience emotional roller coasters while caring for the sick infants.

Dr. Carter's girlfriend makes an impression as she observes ER operations. Dr. Gallant is almost shot during a domestic incident. Dr. Weaver dedicates a center to the memory of Dr. Romano.

Sam treats an abused, pregnant teen. Dr. Carter introduces African girlfriend Makemba to wintertime. ER chaos shocks a risk-assessment expert. Dr. Pratt and Abby restrain a man who has tuberculosis.

Carter misses his pregnant girlfriend who has returned to Africa. A family of four is rushed to the emergency room after suffering carbon monoxide poisoning from their faulty furnace--forcing the claustrophobic Neela to accompany a newborn baby into an extremely uncomfortable hyperbaric chamber.

Dr Morris agitates a patient who then leaves, steals a tank, and rampages through Chicago on his way to County General. He makes it all the way to the ambulance bay before the CPD finally stops him. Sam tries to figure out her relationship with Kovac while Gillian shows up at the ER to cement plans for dinner with Carter, Kem and Kovac - making things that much more difficult. Neela confronts Frank about his arrogant bigotry, bluntly telling him she wants nothing from him but silence from this point forward. During the initial onrush of patients due to the tank rampage, Frank has a heart attack which is, thankfully, caught. Frank's wife and daughter show up and are rushed up to the cath lab where Dr. Pratt is helping Dr. Kayson keep Frank alive. In the end, Neela winds up in the family room with Frank's family listening to them describe a side of Frank that no one has ever seen. Meanwhile Kovac treats a 13 year old with chlamydia and counsels him to contact his sexual partner - which turns out to be quite a few teenage girls.

Carter defends his protégé Neela when Weaver and other doctors rate the residents. Carter urges his student to be more proactive in the emergency room, but Neela goes too far in treating a patient with a brain injury--and sympathetic Gallant errs further by falsifying a medical report. Meanwhile, Chuck protects pregnant Lewis from a pervert who is harassing her. Kovac treats a disoriented young boy whose dad fears that tests will reveal he is not the boy's biological father. Chen is unable to find a caretaker for her combative father. And Corday is uneasy about dating two men at once.

Weaver rushes to the aid of her wife, Sandy Lopez, when the firefighter is severely injured while working and must now battle for her life. Frightened Weaver whispers hope to Sandy by reminding the victim of their newborn child.

Pratt struggles to diagnose a woman who suffers mysterious chronic seizures. An attractive woman, Campbell, informally accuses flirtatious Pratt of sexual harassment. Abby ponders how to get her contentious patients' attention during her psychiatric department rotation.

Carter greets the returning Kem, but their meeting with his father, Jack, gets tense after Carter announces plans for his grandmother's estate.

Carter takes Kem to the hospital to check on their baby since it's not kicking anymore.

Kovacs stops to help a woman and her son whose car broke down. Steve is getting close to Alex, and Sam panics. Abby is looking for her letter whether to see she passed her boards. Pratt shows off his new Chrysler. Elgin tries to build a connection between him and Pratt. Jing-Mei might be battered by her senile father.