Legal clears Izzie to come back to work, but Miranda is surprised that the Chief wants her to oversee Izzie again. She thinks Izzie should get a fresh start, but the Chief makes it clear several doctors on staff have concerns about Miranda's judgment and she needs to prove herself via Izzie.

Miranda takes a hard line with her prodigal intern. Her long lists of "don'ts" includes no surgeries and no being alone with or talking to patients. And she's to be be paired up with another doctor. The first day is none other than Meredith.

Cristina has taken over writing in surgeries on the O.R. board to protect Burke by making sure that he's not booked into the gallery O.R. and that despite bribes from residents, none of them scrub in.

Miranda asks Burke if he's one of the surgeons who doubts her authority because of what happened with Denny and he gives her an offhand reply.

Cristina is too busy prepping for all of Burke's surgeries to listen to Meredith complain that Derek still hasn't called her. So Meredith goes to Derek's trailer and finds him fresh from the shower, with a beautiful woman on his bed!

Izzie is too preoccupied to listen to George's woes: Callie won't even talk to him. So she plays Izzie for him, giving him an optimistic pep talk and he channels Cristina, summing up the Derek situation as, "So McDreamy was doing the McNasty with a McHottie. The McBastard!"

But it turns out that McDreamy's "McHottie" was just his sister, there to check up on him since he's skipped the last few family holidays. She disapproves of Meredith and, much to Derek's dismay, warmly embraces Mark and Addison. She tells Derek that he's never lived alone -- he grew up with four sisters, after all -- so maybe now he needs to take time for himself. So when he runs into Meredith into the stairwell, he apologizes for not having called but says he needs to take some time.

Izzie can't remain a silent observer when she's the only one who thinks that a woman who was studying to retake the bar burned her hand on purpose to avoid the test. Meredith thinks Izzie is projecting her own fear of failure, but when the burn victim inquires how much more severe of a burn would need skin grafts, Meredith agrees. Against orders, Izzie asks the woman if she burned her hand on purpose and she confesses she just didn't want to fail again. They take her up to the psych ward, but she balks, insisting she's not crazy. "We all need help sometimes," Izzie says, and holds out her hand. On her way out of the hospital, the Chief stops Izzie and tells her she's getting daily report cards. And, to her surprise, that she did a good job.

A woman, Noelle, comes in carrying twins -- one in each uterus! She's that medical rarity, a woman with two uteruses. George gloats about the unique case to Alex, who is stuck doing errands for Mark.

They determine that Noelle's two babies have two different due dates, six weeks apart. Which means her fiancé, Greg is just now realizing that she slept with another man when they were broken up and he's only the father of the baby boy. He leaves and she tries to go after him and collapses, jeopardizing the boy, who is due soonest. They take her for an emergency C-section on just the one uterus. Alex, tired of being Mark's errand boy, scrubs in.

The baby girl starts to move and George, who is in charge of making sure that the second uterine wall isn't cut, can't make her stop. But Alex steps in, calming down the girl by talking sports to her, like her father does. Mark tells Alex he's got no future in plastic surgery because he blew him off.

When Noelle wakes up, they tell her the babies are fine. She asks about Greg, but is told he's not there. Confused from the anesthesia, she asks two more times where Greg is and the third time he appears, saying, "Right here." He says he saw his son and asks how "their daughter" is doing.

Picking up a "pig and chicken" metaphor about commitment -- the pig gives everything to breakfast, while the chicken just gives eggs -- from Greg, George tells Callie that she used to be the pig, but now he is. After she realizes what he's talking about, she says he shouldn't say things like that unless he really means it.

A man with a cardiac tumor needs what's called a "Humpty-Dumpty" surgery, which is very complicated. It involves taking the heart out, scraping out the tumor and then putting it back in. Without having told Burke, Cristina has scheduled the surgery later that day. "We are a well-oiled machine," she tells him and convinces him they can pull it off.

Miranda sees the surgery up on the board and puts her name down to scrub in before Cristina can stop her. When no one is looking, Cristina erases it. Miranda sees her name has been erased but doesn't say anything until after the surgery. Afterward, she confronts the clueless Burke. He sees Cristina's stricken face and lies that he couldn't use Miranda. But when Miranda spots Cristina writing on the board later, she realizes who really erased her name.