The fourth season finale of "Grey's Anatomy" began with a montage of death as patients in Meredith and Derek's experimental brain tumor operation fell one after another. It wasn't going well, and Derek was getting upset.
Meredith told her therapist about her mother's suicide attempt. Her mother cut her wrists and bled in the kitchen until Meredith called 911. She said she wasn't upset at her mother, though. Then, in an effort to cheer Cristina up, Meredith gave her the sparkle pager.
Derek told Sloan and the chief that he was looking to make a change by selling his land and moving to the city. Alex, meanwhile, was still taking care of Rebecca, helping her eat, and Izzie was worried that Rebecca wasn't looking very good. Bailey, meanwhile, was trying to see "the bigger picture," taking a new approach to her overloaded schedule. As Callie and Sloan had sex, he talked dirty to the point of helping her envision a three-way that included Hahn.
The doctors were all called to an emergency, but Cristina got to get in on the surgery because of the sparkle pager. The really big trauma was a guy trapped in a solid lump of concrete. Some kids that came in with the guy said they weren't his friends and it was explained that he laid in a bed of wet concrete on a dare to impress a girl.
Meredith and Derek's next brain surgery patient was a cheery teenage girl who happened to be in love with their other next brain surgery patient. The two met in a support group and found out about the clinical trial together. Her parents didn't seem to approve of their relationship as they worried she'd get her heart broken if the boy died.
Later, George was in the chief's office and saw a drawer full of doctors' files. He was tempted, but didn't look. Lexie did later and told him a bunch of information, including the fact that George failed his intern exam by just one point. Rose told Meredith that the legend of she and Derek intimidated her. The chief told Meredith later that only one more patient could undergo the procedure because of the many deaths. Meredith convinced Derek to try to do both of the teenagers' surgeries and she claimed the chief gave clearance, which he didn't.
As the doctors chipped away at concrete boy, he worried that the girl he was trying to impress would always remember him as the guy who was dumb enough to jump into a bed of cement. George was upset that his status as the chief's intern wasn't helping him get into any interesting work, like concrete boy.
When their teenage girl patient tried to walk herself over to her boyfriend's room, Meredith and Derek caught her and brought her back to her own room. Then they played pimps and gave the two some time to "do it" for the first time after the girl told them they never had done "it." Meredith and Derek went so far as to block the door to her room while she hooked up with the dude, and distracted them with papers they had to sign. They wheeled the boy off to surgery and the girl told them not to kill him. That probably made it extra upsetting when the boy. Derek, furious, threw away the bottle of champagne he and Meredith were meant to use for celebration after the trial's first success. When the girl still insisted on going through the with the surgery, Derek became even more angry. He worried it would fail and was upset at Meredith for encouraging it. He said he never wanted to see her again after the surgery was over. "We're done," he told her.
George got upset with Lexie for telling him that he was just one point away from passing his intern exam. Izzie told Alex that Rebecca needed to be admitted to the hospital after she tried to cut herself with a kitchen knife. Alex snapped at Izzie, calling her a "stupid bitch." Later, Izzie had to fight back, as Rebecca's doctor, and threatened to have Alex arrested if he interfered with her treatment of Rebecca. He told Izzie that he could take care of Rebecca, just like he'd taken care of his mother. It seemed like he wanted a second chance, saying, "I was a kid then, and I'm a man now, so I'll be better at it." In the end, Alex told Rebecca she had a personality disorder and needed more help than he was able to provide.
Sloan continued to egg on Callie about her desire to hook up with Hahn. Derek told Rose that the clinical trial was making him a failure and that he never wanted to do it. He said, "I fail her over and over and over." Rose corrected him, saying he meant to say "fail them" as in, the patients. He didn't respond.
When cement boy when into cardiac arrest, Bailey wanted to wait for Hahn to arrive before cutting him open and performing an embolectomy, but Cristina stepped up and said she could do it. She'd done it before with Burke. When Hahn showed, things got interesting. Hahn started criticizing Cristina's work, but Cristina had good reasons for everything Hahn said she'd done wrong. As Hahn kept talking, Cristina finally said, "Shut up and let me work." Hahn looked at the chief, who said, "Let her work, Dr. Hahn." Oh, snap! Later, the chief piled it on, telling Hahn she needed to be a better teacher and that she should have been proud of Cristina going solo on a complicated surgery. The chief hadn't seen that Cristina was in the room and heard the conversation. The chief told her not to make him regret backing her up.
George, who was still trying to work hard to impress the chief, snapped back when the chief told him "good job" after George watched cement boy overnight. George said "it's not a good job for me because I'm better than that." He made a case for himself being a good doctor and the chief ultimately agreed to give George a second chance at his exam.
Meredith blew off the chief when he questioned her about going ahead with two surgeries even though he said they could only do one. Then she got in his face about her mother's suicide attempt and told him that her mother was distraught over him. He said he was sorry. Meredith told the chief that her mother was a talented, gifted, extraordinary surgeon, and that meant she wasn't really trying to kill herself. If she'd wanted to, she could have. She told the therapist her realization and the therapist told Meredith that she gets to learn from her mother's mistakes.
Cristina said she was drunk with power from having the sparkle pager, and she decided to become the teacher and show Lexie how to do a whipstitch.
Derek and Meredith's patient was still sleeping after her surgery when Meredith looked at her X-rays and found that the tumor was getting smaller. It worked! Rose was with Meredith when she figured it out, and Meredith suggested that Rose tell Derek. Rose told Meredith that it was the kind of news he'd want to hear from her instead. Meredith ran looking for Derek, but couldn't find him, and the champagne bottle wasn't in the residents' lounge refrigerator. Derek saw the patients' parents crying and that was how he found out the good news. He went and took the champagne bottle out of the trash and set out to look for Meredith.
Bailey handed Izzie the keys to the clinic, but was giving her the entire clinic. Bailey said she realized she couldn't do everything she wanted to do, and she wanted to focus on surgery, so she entrusted Izzie with the clinic.
The chief told Meredith that he knew he was the villain in her story about her mother, but insisted he's not a bad guy. Sloan suggested that Callie go try things out with Hahn, since she was clearly interested, and she kissed Hahn -- like, seriously kissed her. And that began a whole string of kisses, for better or worse. The chief went to talk to Adele and told her he wanted to be back with his wife. She welcomed him and they kissed. George burst into the apartment he shares with Lexie and gave her a friendly, jubilant peck on the lips. Izzie tried to console Alex about Rebecca and his mom, and he leaned in and kissed her. That ended sadly, though, as they kissed for a moment and Alex just broke down crying. Bailey, turned off the lights to the clinic and picked up her little boy, gave him a kiss on the cheek and said they were going home to see daddy.
Derek finally found Meredith. She was standing in an outline of their future home that she's laid out on the open spot on Derek's land that overlooks the city. She said she went and "got all whole" and Derek wasn't there, so she was mad at him. But then, they kissed. He stopped, though, and said he needed to go talk to Rose so his conscience could be clear. He asked Meredith to wait for him, then walked away.