What I am is what I am. Are you what you are, or what?

That's the theme of tonight's episode, and the question of the hour. It's the one posed by Edie Brickell, whose lyrics give the episode its name, and asked by the doctors of Seattle Grace -- of one another, and of themselves. It all starts with Meredith wondering who she is... and lately, why she's throwing up all the time. No, she's not pregnant. She has appendicitis.

As a result of her condition, everyone finds out exactly what is on the mind of Meredith Grey. She gets high, and not on life. Serious painkillers leave her in a talkative, amusing and often awkward daze. As she's being prepped for surgery and babbling incoherently, Meredith opens up to Addison about Derek, wanting to know how she knew he was the one, among other things.

Derek and Finn both come to Meredith's side. After receiving a stern warning from Mer's new friend, Addison, not to hurt the impressionable again, and realizing what a superior guy Finn is, Derek decides to be the bigger person and bow out. Only then does Dr. Grey make her long-awaited choice... and send the dejected McVet packing for good.

She may be making a mistake, but he's the one.

The staff learns a lot more about who Mark Sloan is, too. A jerk! His first order of business as Seattle Grace's new plastic surgeon is to order Alex to get him a coffee. Next up? Disrespecting Dr. Bailey. Following that? Making both Addison and Derek extremely uncomfortable. Yup, McSteamy's back and in full effect.

After a car salesman burns his face lighting a cigarette while hooked up to an oxygen tank, Derek and Mark spar over his treatment. As both McDoctors know full well, it's personal. Ultimately, Mark does his best to reconstruct the man's face, but it's Dr. Bailey who really comes through, reassuring the patient that a face doesn't make you who you are -- even if you do sell cars for a living.

Meanwhile, Dr. Burke bluntly tells Cristina what he is: Nothing. Without his hands, at least. Despite Dr. Yang rushing him to get better, and Shepherd clearing him for surgery, Preston knows his hand is still trembling and he can't hack it in the O.R. He ends the episode practicing on a cadaver and struggles with the tremor yet again. After an outburst, Cristina helps him complete the mock surgery, but his recovery remains in doubt.

The deterioration of her marriage, an epic bender and the downright shock of Mark joining the staff proved too much for Addison, who uncharacteristically lets herself be bossed around by a patient intent on natural childbirth, and who needs a Caesarian section immediately.

Following her unexpected heart to heart with Meredith, and a little prodding from arrogant Alex, Dr. Montgomery Shepherd steps up to the plate and saves the woman's life -- and her baby's.

George and Callie find themselves at a crossroads when, once again, he can't talk about his feelings or make himself available -- except where Meredith and Izzie are concerned. After scrubbing in on Meredith's appendectomy, he bails on a date with Callie to be with Izzie. That doesn't go over well.

Upset at playing second fiddle to Dr. O'Malley's friends for the umpteenth time, Callie tells him not to bother calling. She then proceeds to Joe's, where she picks up a dark, handsome type by the name of Mark Sloan. Really.

The biggest mystery revealed on this Seattle day, however, is that of Mr. Denny Duquette. Senior. That's right, Denny's father comes to Seattle and meets Izzie. She gives him the complete rundown of how they met and fell in love... and how Denny died. He's adversarial at first, demanding to know what happened and determined to protect his son.

Denny Sr. comes around when he gets to know her. In turn, Izzie learns that Denny Jr. disappeared from his folks on the worst of terms, essentially bidding them farewell and stating he was going away to die.

But that's not all.

Immediately after receiving his successful heart transplant, he left Denny Sr. a voicemail telling him about the operation and the incredible girl who made it happen. With George by her side, Izzie listens to Denny's poignant message while opening an envelope Denny Sr. gave her, learning for the first time that Denny established for her a trust fund.

Worth $8.7 million.