To begin the first of a two-part season finale, House was getting a lap dance in a strip club with no idea how he got there. He knew immediately that he'd lost some memory and eventually noticed that he was bleeding from a gash on his head. He didn't remember much, but he was sure he had to save someone's life.
It didn't take long before House was recounting the fact that he'd been on a bus when it crashed, but he was still having troubling recalling several hours from the previous night. He knew he had to save someone who was on the bus, so he began wildly checking everyone who'd been on the bus for any possible symptoms. He went so far as to announce that a patient had meningitis so he shut the emergency room down and check everyone. He quickly suspected the bus driver had a seizure, and he was right -- sort of.
House looked at hospital security camera footage and any other clues he could find to trigger his memory. Kutner suggested medical hypnosis and Chase just so happened to have had some training back in Australia. The hypnosis sent House into a bizarre world of memory and hallucination that included seeing visions of Amber in a bar. Wilson was with House as he recalled these memories and House nearly told Wilson that he wanted to see Amber naked in his fantasy. But he didn't. After that, House saw some of passengers' faces from the bus, including one of a mysterious woman who caught House's eye. After misdiagnosing a goth kid who'd been on the bus, House went back to the bus driver, who suffered sudden paralysis.
While conducting an MRI on House, Wilson asked him what he'd been hiding from his vision of Amber. House finally told Wilson it was that he wanted to see Amber naked, which didn't surprise Wilson because House wants to see everyone naked. The fact that House didn't objectify Amber in his fantasy gave Wilson a warning that House had feelings for Amber. "This is bad," Wilson said.
House became obsessed to the point of endangering his own life, due to his cracked skull, in his quest to save whomever it was from the bus that he was trying to save. But he didn't know why.
House submerged himself in a bath to deprive his senses in yet another effort to recapture some memory. This is where it got interesting. He slipped into a fantasy that included Cuddy doing pole dancing and doing a strip tease while they discussed possible diagnoses for the patient. That was, umm, different. The bus driver appeared in the hallucination, offering up some diagnoses of his own, and the mystery woman showed up, as well, when House was yanked from his bath and sent home with a nurse and security guard. He continued to lead the team in treating the guy over the phone until Cuddy finally asked him to return to the hospital.
House noticed caps on the bus driver's teeth and thought he might have had an air bubble enter his gums during recent dental work. He locked himself in the man's hospital room with Thirteen while Cuddy, Foreman, Kutner and Taub watched helplessly. House wanted Thirteen to stab the guy's heart to get the air bubble out. With Cuddy shouting at Thirteen, calling her Dr. Hadley, Thirteen jammed a syringe into the man's chest and saved him.
Cuddy went home with House, but only to make sure he didn't do anything stupid. She slept in the living room while he stayed in his room. But a middle-of-the-night dream brought the mystery woman back to House and gave him some clues to solving the real puzzle he had yet to figure out. She had a necklace charm, a red scarf that he was meant to tie around her. As he did it, she said, "I'm cold," and House replied, "Stay with me," without knowing why. House woke up knowing that the mystery of the real person he was trying to save was still unresolved. The bus driver's air bubble was just a coincidence and was actually the result of the bus crash, not the cause of it.
House staged the scene inside the bus using nurses and doctors from the hospital to represent passengers. Meanwhile, he tossed back pills that are meant for Alzheimer's patients to help charge up his brain. Cuddy and Wilson worried the pills could make his brain go into overdrive and blow up his heart. The scene went dark and House saw the mystery woman again. She told him she was providing clues to the real mystery. It turned out, her necklace was made of amber, which triggered his memory of Amber being on the bus at the time of the crash. He relived the crash and saw Amber tossed around in the bus. She had a metal pole lodged in her leg. After the crash, he saw Amber and tied a red scarf around her leg. "I'm cold," she told him. "Stay with me," he said. Then he lost consciousness and the next thing he saw was a medic carrying Amber out of the bus.
House's heart stopped from all the drugs he'd taken, and when he came to he said, "Amber." He told Wilson Amber was on the bus. Wilson realized he hadn't spoken to her since the crash and Thirteen confirmed that "Jane Doe #2" had a birthmark on her right shoulder blade, which Amber does. House told Wilson Amber was on the bus with him and "she's the one who's dying."