Guilt. It never travels alone. It brings reinforcements, namely its close friends doubt and insecurity. And it packs a wallop.

At first, when they are told to attend the staff's M&M (mortality and morbidity) meeting, Cristina and the other interns are psyched. That all changes when Dr. Bailey comes under intense scrutiny from her colleagues for her role in Denny's death.

Her guilt over the case lingers... and manifests itself in her multi-layered treatment of a conflicted breast cancer patient. By reaching out and sharing her own guilt with the patient, Bailey is able to steer her towards a life-saving mastectomy.

The largest amount of guilt -- empirically speaking, anyway -- belongs to Izzie. With a check for $8,700,000 waiting to be cashed and the chance to do anything she wants with, Dr. Stevens can't get past the feeling she doesn't deserve this wealth.

Determined to walk away from Seattle Grace forever after Denny's death, Izzie has a change of heart (no pun intended) when cleaning out her locker and speaking with Dr. Burke. When Izzie remarks that everything will be fine, Preston snaps back at her.

In Preston's mind, her real guilt should not be harbored over Denny dying, or even indirectly getting him shot, but for wasting her talent. Izzie walks over to Richard's office, where the Chief shares his own experience as an intern who made a fatal mistake -- and we're led to believe Izzie will be back practicing medicine soon.

NOTE: The un-deposited check is still on the refrigerator in Meredith's house. Izzie is insane.

Dr. Burke, meanwhile, is battling is own inner demons even as he helps Izzie exorcise hers. Unable to tell Richard that he's not the same Dr. Burke, he's called in on an emergency surgery and relies on Cristina's assistance to make it through. The persistence of Preston's tremor is troubling, but the newfound courage of Dr. Yang is heartening.

The patient Burke and Cristina saved was a man who suffered a heart attack after having sex with his ex-wife... and getting stuck inside her. There was a piercing involved. We would go into more detail but it's kind of gross. After Addison and Meredith separated the lovers, he was rushed to the OR, while the ex-wife discussed her adulterousness with Addison.

The timing of this is not without irony, as Addison had officially ditched the Shepherd portion of her name that morning. After finalizing a divorce with Derek on amicable terms, Addison is suddenly stricken with guilt over his not knowing the true nature of her relationship with Mark. The patient vows to confess to her cheating, and Addison decides to follow suit.

It doesn't go well. Derek says he never wants to see her again.

Meredith, meanwhile, can't seem to tell Derek that she dumped McVet. This is probably because she feels bad about his marriage's failure, and wants to give him space. It's complicated, as we know very well by now.

The sad news, for Mer, is that by the time she works up the courage to tell him, he's just had the A-bomb (A for Addison or adultery, take your pick), dropped on him. He walks away in a daze, with little of consequence to say.