From a whisper to a scream. Essentially, that's the crescendo taken by Cristina and Preston regarding their secret. The tension boils from the very beginning... as evidenced by the fact that Cristina jogs (even though she doesn't jog) over to see Meredith.

Dr. Grey and Dr. Shepherd are still adhering to their "no sex" policy so Cristina isn't interrupting much of anything when she barges into Mer's bedroom early in the morning and demands to talk to Meredith. Alone. She asks Meredith a confusing, hypothetical question about Derek robbing a bank and Meredith driving the getaway car, and pondering whether Meredith would then turn herself in if Derek were discovered.

But before Meredith can figure out what she's really saying, Cristina takes off. At the hospital, she voices her fears to Burke that George will reveal their secret to the Dr. Webber. Burke tells her it'll be fine, because he hasn't had a tremor in a week and that they're still a strong team. That's when all the interns are paged to the emergency room. A older driver just plowed into the fish market and there are at least a dozen victims.

All hands are on deck except Izzie, of course, who's assigned to watch George's father.

The elderly Mr. Dickerson was driving the car that caused the accident, but his wife says that the accident wasn't his fault because he just couldn't stop the car. Police are waiting to take her statement, but she insists on staying with her husband and talking to them later.

Cristina watches as Burke works on a patient without her, especially since his medical school rival at Johns Hopkins, Dr. Hahn - the surgeon fans may recall him taking Denny's heart from in the tension-filled season-ending episodes last season - is now on the premises.

A woman named Janelle, covered in blood, walks into the ER and collapses in Addison's arms. She was thrown through a plate glass window during the fish market accident. She's also 10 weeks pregnant, so Addison and Mark both try to ensure that she and the unborn child will survive.

Mrs. Dickerson, who is one of Janelle's best customers at the market, asks how she's doing. Janelle then starts coughing up blood, and a test reveals that she has a shard of glass in her heart and needs to be operated on now.

Izzie is singing Burke's praises to Mr. and Mrs. O'Malley (and revealing more than a few details about his love life), but George is markedly less enthusiastic. Izzie asks what's going on and he tells her to stay out of it. He asks Dr. Hahn, who works at Seattle Presbyterian but is at Seattle Grace for a consult, to do the operation on his father instead.

Cristina sees Dr. Hahn and Richard in Mr. O'Malley's room. When Richard tells Cristina that he needs to take to Burke immediately, she assumes the worst and that Richard may be asking Dr. Hahn to replace Preston entirely.

Meanwhile, George's parents reschedule the operation so Dr. Burke can do it after all, since Izzie has been telling them he's the absolute best. George loses it and informs them why Izzie is there - she's on probation because the last time she treated a patient (Denny)... we all know what happened.

Callie tries to inquire about George's dad, but he reminds her they broke up and that he knows about her sleeping with Mark. She assumes Meredith told George, so she slams her against a locker. Meredith says she didn't even know who the other person she slept with was until George told her. Callie finds George to try to explain that she slept with Mark only after they broke up, but he tells her he can't deal with this right now.

Mr. Dickerson's scan reveals a subdural hematoma and an advanced case of spinal stenosis, which means he probably couldn't feel his feet and definitely should not have been driving. Derek wonders why Cristina is acting oddly, such as disappearing since she's supposed to be his intern today. Burke and Meredith both feign ignorance.

Cristina tells Burke the Chief is looking for him, and that they need to get their stories straight. Burke says he's just going to tell the truth. But it turns out Richard is retiring, and he wants Burke to replace him as Chief of Surgery. Burke tells Cristina that he's wanted this whole life, but now it has blood on it. He says he crossed a line, and that Cristina is the one who dragged him over it.

Mrs. Dickerson insists there was nothing wrong with her husband before the accident, but when she sees Janelle being taken into surgery, she confides to Miranda that she did know. It parallels the Burke-Cristina drama well. Their daughter took away his car keys, but not giving them back would have felt like a betrayal. Miranda tells her she needs to inform the police.

Derek invites Burke to scrub in with him on Mr. Dickerson. Burke is on the verge of telling him the truth when Alex says they need him right now to operate on Janelle. Burke tells Derek to get Dr. Hahn to assist him, and he'll take the other operation. He instructs Karev to make sure Cristina scrubs in with him.

After removing the glass shard, Janelle's heart is on bypass when Meredith comes in to say they need Burke to work on Mr. Dickerson's heart, which has a tear in it. Dr. Burke tells Cristina to stay with Janelle, but she follows him out anyway and Meredith realizes Cristina thinks Burke can't operate without her. Cristina reluctantly goes back to Janelle.

Meredith spends the rest of the Dickerson surgery watching Burke operate, not Derek. Burke returns to Janelle but there's a complication and his hand seems to be cramping up. When Cristina starts to question him, he orders her out. After the surgery, he goes to tell Richard that they need to talk and he agrees, because Cristina is already sitting there.

Running into each other in the elevator, Derek asks Preston why he didn't tell him, since he thought they were friends. He coldly replies that he thought Derek was his surgeon. Derek realizes Meredith knew before he did, since she was watching Dr. Burke operate and not him, but she says Cristina is her best friend and she couldn't tell him.

That night, when Cristina finally goes home, wallowing in defeat and in an uncertain future, Burke closes the bedroom door in her face as the credits roll.