Grandpa Mark: When Lexie performed an ultrasound on Mark's newly discovered teen daughter, Sloan Reilly, she discovered that strands of amniotic tissue were wrapped around the baby boy's legs. Left to develop, they might end up costing the infant at least one of his legs. Mark of course calls the one expert neonatal surgeon he knows — and once had a fling with — Addison Montgomery, from spin-off "Private Practice." But during the surgery, Mark panics that his daughter will die and won't let Addison complete the procedure. In the end, he takes his teen daughter back to Addison's practice in Los Angeles to complete the crossover episode.
Before he goes, he and Lexie apparently break up when she realizes Mark's new daughter and her coming baby will have to come first in his life. But then both of them wind up moving in with Derek and Meredith, because none of the doctors in this show seem to make enough money to buy their own homes.
Heart of hearts: Owen's Iraq pal Dr. Teddy Altman gives Cristina a chance to replace a heart valve, a surgery Cristina is thrilled about. Once the slightly neurotic heart patient finally picks the kind of valve she wants (pig, not mechanical or bovine), Yang plunges into the surgery, but once it starts to go bloodily wrong, Teddy just stands back and lets her flounder. Owen storms into the operating room, thinking Teddy is letting Cristina kill a patient simply because she doesn't want Cristina and Owen to be together. But when Teddy announces she's leaving Seattle, Cristina runs after her and begs her to stay, saying she's the only person who believes in Cristina more than Cristina herself, and even agrees to give up Owen to Teddy.
Taken out of the game: When a promising pro quarterback gets a tough hit and winds up at Seattle Grace, he has a panic attack. Derek discovers that ever since the player's son was born, the man's felt fear on the field and no longer wants to play. To give him a face-saving way to back out, Derek and Callie perform a knee replacement, effectively ending the man's pro career.
Talk about a merger: Mercy West transplant Reed coaxes Alex to let her scrub in on a surgery with a promise of "drinks and you know," ticking off her Mercy West pal Charlie. A furious Meredith makes sure Reed knows that Alex and Izzie are still married, which doesn't seem to bother Reed that much. But in the end, Alex is the one who says he doesn't trade surgeries for sex. This show hasn't really missed Izzie that much, to be honest.
Midnight confession: Derek is confused by all the time Meredith is spending with the chief, and in true Meredith fashion, she's stammering and making excuses. But they're doing thrilling things together, such as watching old surgical films of Meredith's mother operating. Finally, Meredith confesses to Derek that the chief is drinking again.
Single mom: In perhaps the dullest and weirdest story line, Derek keeps trying to set up Bailey with men. But when one of them asks her out, she spews out a long confession of all the woes in her life (3-year-old Tuck was potty trained, but now with all the family drama, he's not) and completely scares him away.
Quote of the night: "Yang's killing her patient and Altman's reading the Atlantic Monthly." —Alex to Owen, as Cristina's surgery goes south.
Runner-up quote of the night: "He doesn't have a dad, and he has a stupid, slutty mom. ... He needs feet." — Mark's pregnant daughter, Sloan, talking about her unborn baby.