For those that missed it and are asking what happened...
Last Week: Carter comes back and goes straight to Abby's she pretty much says, give me my key back and leave. There is massive construction going on at the hospital and everyone is really pissy. A young carpooling mom blacks out and flips her car, she and 3 kids are in the ER. A new med student (girl from Bend It Like Beckham) joins cast. Dr. Pratt is flirting with her and it makes Dr. Chen mad. The young med student finds out the mom has some rare blood disorder right before they were going to do something to her that would have been bad for her condition (sorry forgot what) and because of med student she lives. Dr. Romano had his arm removed. The young med student was supposed to be watching this older woman, under Dr. Gallant's (who just earned the title) care, she gets sidetracked and someone moved the old woman. They later find her bleeding out from an arm wound, and the young med student is very upset. Carter and Abby try to have a conversation but things aren't going well. The phones get messed up by the construction so they are not answering them, young med student answer the phone and tells everyone that Kovac has died. Carter decides immediately to go back to the Congo and "borrows" a large duffle full of medical supplies to bring back with him. He and Abby leave on a bad note.