Grey's Anatomy, Season 6

The Seattle Grace staff continue to mourn George's death; George's mother arrives but is unsure of what to do with his organs.

The Seattle Grace staff continue to mourn George's death; Derek receives a proposition from the hospital board.

Izzie returns to work while the Seattle Grace residents fear possible layoffs; Bailey and Alex's difficult case is further complicated by her schizophrenic son.

Meredith tries to save the life of her father, who comes to the hospital with a failed liver; Izzie empathizes with a patient riddled with tumors; Mark tricks Cristina into assisting on an unusual surgery.

The residents of Seattle Grace and Mercy West vie for their careers as the hospital merger begins; Arizona stands by enraged Callie.

After a burn victim unexpectedly dies in the ER, the Chief and board member Jennings question the residents, as all the staff members defend their actions in an effort to save their jobs.

When Isaac has an inoperable tumor wrapped around his spine, he turns to Derek who, despite the Chief's objections, decides to move forward with the risky surgery.

The parents of Arizona's 10-year-old patient offer the hospital a generous donation, but Arizona finds herself in a conflict of interest when the patient's condition worsens; Cristina tests her boundaries with Owen.

Owen recruits a fellow Iraq War veteran to be the new cardiothoracic surgeon, but Cristina questions the new surgeon's abilities; Izzie returns with her high school mentor seeking treatment for dementia.

As the holiday season passes, Miranda is visited by her father, who disapproves of her life choices; Mark and Lexie must cope with the arrival of a woman from his past; Thatcher questions the chief's recent behavior.

Addison returns to Seattle Grace to perform a procedure on Mark's pregnant daughter; Cristina is assigned the lead on a complicated surgery.

After learning about Richard's drinking problem, Derek confronts him; Izzie returns, hoping to reconcile with Alex; tensions run high for Teddy, Cristina and Owen in the aftermath of Cristina's startling confession.

Derek faces a lawsuit on his first day as interim chief when a patient awakens from anesthesia during surgery; Mark refuses to speak to Lexie.

The doctors treat dozens of people when the roof of a romantic restaurant collapses on Valentine's Day; Meredith struggles with her new duties as the chief's wife.

Callie, Bailey and Richard present pivotal surgical cases from their pasts when Derek restores the hospital lecture series.

A famous surgeon is rushed to the hospital; Callie and Arizona try to help Teddy and Sloan move on from their pasts.

Owen and Richard compete for an extremely difficult surgery; Bailey gets ready for another date with Ben.

A patient's desire to end her life triggers haunting memories for Hunt; Arizona and Callie have different opinions about the future; Richard tries to adjust to his new role.

When Alex's brother shows up at the hospital with a hernia, Alex must get Bailey's approval for pro-bono surgery; parts of Alex's past are revealed to his friends and colleagues.

Mark, Teddy, Callie and Arizona help Sloan deliver her baby; the doctors treat a crab boat captain who was stabbed with a giant shark hook.

Bailey preps the team with mandatory sensitivity training prior to admitting a 700-pound patient and the case proves to be challenging in every sense of the word.

All reassess their personal lives after witnessing a chance reunion between two long-lost lovers in the emergency room; Karev treats a troubled teen; Meredith shares her suspicions with Cristina.

The hospital is hit with an unprecedented crisis; Meredith and Cristina's surgical skills are put to the test.

The hospital is hit with an unprecedented crisis; Meredith and Christina's surgical skills are put to the test.