There's no mystery about this Grey's Anatomy episode's title, "Heart-Shaped Box." The episode literally stars a heart inside a box — it's a heart waiting for a transplant, and the machine encapsulating it is keeping it warm, beating, and alive. And the doctors — namely Cristina (Sandra Oh) and Richard (James Pickens Jr.) — not only anthropomorphize it, but make it their profession guru.

Richard tells Cristina to let it be the "key" to her surgical wish list, and she starts posing questions to it. It turns out she isn't actually trying to converse with an organ, thankfully; she's just using the case as the golden standard against which to judge all prospective dream surgeries. (Phew. That's one shark Grey's didn't jump!)

Meredith (Ellen Pompeo) is nervous about her and Derek's (Patrick Dempsey) upcoming parental rights hearing. At the hospital, Bailey (Chanda Wilson) tells her that they have a VIP patient: Louise O'Malley, George's mom. Louise is having complications following a gall bladder operation, and Mer finally figures out that a length of cystic duct was left inside her body. Mer convinces Bailey to let her cut, and Bailey even gives Meredith advice about the hearing. (She tells Mer to wear a sweater set to look warm and motherly.) Aww, can they please just hug it out and be friends?

Louise's return to Seatle Grace makes Alex (Justin Chambers), Mer, and Cristina reminisce about George. But one person is affected more than the rest: Callie (Sara Ramirez), whose whole life has changed since she and Louise last spoke. Callie dodges introducing Arizona (Jessica Capshaw) as anything other than "Dr. Robbins," and Arizona is surprisingly cool about it, telling Callie that she doesn't need to come out to Louise. But Callie is there at Louise's side when she wakes up from her (successful) surgery, and she does come out, and Louise is elated by Callie's newfound happiness.

Jackson (Jesse Williams) is still leery of Lexie's (Chyler Leigh) fixation on Mark (Eric Dane), and his jealousy compromises his job performance: he avoids a surgery that he and Mark were excited about. Mark is rattled, thinking that he lost his partner-in-crime. Finally, Jackson leaves Lexie and, choosing to focus on his career, reconciles with Mark. Time to bag and tag that romance — it's dead.

Meanwhile, Lexie has her hands full with Derek's patient Justine (played by Alfre Woodard), a novelist who's way more eager to finish her successful time-travel-romance book series than she is to have her leaking aneurysm clipped. To expedite the process, Lexie starts typing up the novel as Justine dictates, and she gets totally swept up in the story's romance. But then, suddenly, Justine's aneurysm blows and she's rushed into surgery, which she and Derek rock.

Derek's new passion project is finding brain patients without hope — patients to whom all other doctors have said "no" — and saying "yes" to their cases. Owen (Kevin McKidd) is wary, warning Derek that his arrogance could cost him his reputation. But Derek can be quite head-strong. (Hah!)

Elsewhere, Arizona spurns a prospective pediatrics fellow by raving on and on about Alex. And Teddy (Kim Raver) is frustrated when Henry becomes interested in med school — but before they can work it out, he starts violently coughing up blood. Tedry! Hendy! Whatever you two are called! We're seriously freaked here. You can bet we'll be tuning in next week.

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