"Holy ... !"

The episode ends with Meredith exclaiming that word under the most mind-blowing of circumstances. Let's take a look at how she got there.

We begin the hour with the title character sinking into the abyss. She has so much more to say, Meredith tells us in her opening narration, but she's disappearing. On land, no one can locate her, although people are starting to worry.

The patient whose leg Meredith treated is brought over to the triage area, where Derek spots Meredith’s jacket and ID tag on him. He gets worried and goes to find her, asking the little girl to show him where Meredith is. It takes her a minute amidst the chaos, but she slowly (and ominously) points towards the water.

Meanwhile, Izzie is still with the man who was trapped under a car. When she begins to panic, one of the unconscious man's friends calms her down and she calls the Chief for help. Richard tells her she has to drill holes in the man's man’s skull. Using Vince's drill, and with Mark and Richard talking her through it via cell phone, Izzie handles it like a pro and the pressure in the man's brain is eased.

The rescue people finally arrive and the man makes it to Seattle Grace. Alive. Richard tells her she saved the man's life and is officially off probation - now get ready to scrub in on the man’s surgery and use the actual surgical drill this time.

In order to get the injured mother to calm down before surgery, George lies and tells her he found her son. Bailey tells him be had better go actually find the kid before the mother wakes up. George searches the hospital, top to bottom, including the morgue. But he can’t find the kid.

Finally he sees that there’s a 7-year-old John Doe in the O.R. and that Callie is operating on him. He asks Mrs. O'Malley to please look at the picture he's carrying to see if the kid she’s operating on is Chris. At first, Callie doesn’t want him bothering her, but she eventually looks at the picture and confirms that it’s her patient. Phew!

Alex, for his part, is still trying to figure out who the pregnant woman he saved is, while fielding 500 questions from patients' family members at the same time. At first he can’t handle the situation and only has a 2-hour-old list to show them. Finally, with Sydney's help, he comes up with a system to give the people updates.

After Addison ponders her own place in the world - would anyone notice if she went missing? - Alex and Sydney take Polaroid photos of the patients and post them on the wall for the friends and family to come and identify. He heads down to the morgue and takes photos of the deceased victims as well. Fearing for the worst, he finds the body of a pregnant woman and takes a picture.

When he returns to the clinic, he talks to a man who said he was looking for a pregnant woman. Alex is hopeful that the woman the man is there for is the Jane Doe in the O.R., not the one in the morgue. He describes the woman in the O.R., but the man says it doesn’t sound like her. Nor does it look like her in the picture. Alex then confirms that she is dead, and the man is inconsolable.

Emotionally and physically drained, Alex just stands there, looking around the clinic at all of the people crying, hugging one another or in hysterics on the phone breaking the news to others. Afterwards, he goes up to Addison and tells her that he’d notice if she disappeared.

Cristina has been stitching people up all day in the pit, but she's really focused on "her person." Meredith. She's concerned Mer is missing, but Yang also needs to tell her about the engagement before it becomes real. That's how her mind works. She has another argument with Burke on the subject, in which she explains her relationship with Meredith.

As only Dr. Yang could put it and make sense, she says that if she killed someone, Meredith would be the one she’d call to help drag the body across the floor. Preston isn’t happy that she’s comparing their engagement to a corpse, and leaves. What Cristina is trying to say is that nothing is real until she tells her best friend.

Which brings us back to the missing Dr. Grey. When we next see the little girl, she’s standing alone by the water. As a Coast Guard member finds her, he begins to carry her away when Derek climbs up onto the dock, carrying a blue, seemingly lifeless Meredith in his arms. He performs CPR on her in the ambulance, but she’s not responding.

As the doctors frantically try to revive the blue Dr. Grey, Richard orders Derek out of the room. The devastated Dr. Shepherd slumps down on the floor of the hallway, inconsolable. Mark comforts his former best friend, while Preston asks what he can do to help. Derek responds that what he needs is for Preston to get in there and fight for Mer's life.

As Addison, Burke, Webber and Bailey work on Meredith, Addison makes some suggestions about how to get warmth back into her frozen body. But as hard as they push, and despite the repeated CPR, shots and other measures, the doctors can only raise Meredith's body temperature from 80 to 82 degrees. Panic ensues. Meredith goes into cardiac arrest and we hear the familiar drone of the flat-lining EKG.

"We're losing her," the Chief says.

We then go inside Meredith's head, where she's moving towards the light - literally. On the other side, she awakes - still in a hospital room, in blue scrubs - but totally lucid. Except that flanking her are a pair of former acquaintances who are no longer among the living. To her left, we see Dylan Young of the bomb squad. To the right, none other than Izzie's late fiance, Denny Duquette.

"Am I dead?" Meredith asks.

"Damn right you are," replies Denny.

As the realization hits and Meredith abruptly sits up in disbelief, the credits roll, leaving us in a state of shock - and bewildered as to what will transpire next.