S10, E11: Carter returns to County General to hearty welcomes. Although Abby is shocked to learn that Carter's beautiful African girlfriend, Kem (recurring guest star Thandie Newton), is already pregnant with Carter's child, Abby has moved on with her life as well, going back to medical school. Meanwhile, Pratt's day starts off badly when Gallant finds out that Pratt has been having sex with Valerie (recurring guest star Joy Bryant), Gallant's attractive sister. Frustrated Pratt is repeatedly overruled on medical decisions until he heroically keeps an accident victim alive while a vital MRI is taken. But Pratt then rashly attempts to intubate the patient's son, who suffers from osteoporosis, and ends up breaking the young man's neck, permanently paralyzing him. Also, Kovac informs Weaver that he is quitting to return to Africa. And Sam feels like she neglects her young son, who is misbehaving in school.