Sidney was brought to Princeton-Plainsboro Teaching Hospital when she was nearly hit by a vehicle while out jogging. It was soon determined she was disoriented and suffering from amnesia. Dr. Cuddy sought out Dr. House for a consult. He was told that despite her symptoms, the MRI showed no abnormalities. She was not carrying any identification, but was wearing a heart rate monitor. Dr. House looked at the patient and realized she was well off - her running shoes cost $400 a pair. He figured someone would come looking for her. The patient asked for something to eat. The nurse said she had just eaten 15 minutes before and had forgotten. However, Dr. House realized patients ask to eat because they are hungry. He figured she might have some sort of metabolism problem as she had the physique of an extreme long distance runner.
Dr. House examined the patient’s scans and found a subtle lack of differentiation between white and grey matter in the brain where memory is controlled. Dr. Hadley thought it might be bacterial infection. Dr. Chase thought it might be multiple sclerosis and Dr. Taub thought it was trauma. However, all of these were soon ruled out. Dr. Chase thought the most likely culprit was a toxin, making an environmental scan imperative. The only clue they had to her identity was her heart rate monitor, which had a serial number, meaning it could be traced. Dr. House agreed to take the patient there himself.
Dr. House went with the patient and his friend Mr. Alvarez to the store that sold the monitor, but they didn’t recognize the patient. The patient didn’t recognize any of the surroundings. However, when Mr. Alvarez suggested they take a break for donuts, Dr. House realized that a distance runner may eat them. Sure enough, the clerk recognized her. Although she didn’t know her name, she had a business card from the man who was with her, who they figured was her boyfriend.
They called around and they finally found the patient’s husband Jay who identified her as Sidney. He had called the police, but they said she hadn’t been missing long enough. He had called some hospitals, but PPTH seemed too far away on foot, so he hadn’t called them. The patient had a large trophy case. As they told her about her life, she didn’t seem to think she was like that. Dr. House noted that Sidney seemed more comfortable with him than with her husband. The husband seemed to realize this too. Mr. Alvarez collected a number of samples, and the husband said she was working with clients whose houses were contaminated with methane. Dr. House planned to take her back to the hospital to check her blood and urine and start treatment for methane exposure. However, when they started back to Dr. House’s car, she lost her balance. She complained her foot had gone numb and Mr. Alvarez noticed her pants were wet, indicating incontinence. Dr. House realized she was having complex partial seizures. That ruled out methane and the toxic samples Mr. Alvarez had collected. A seizure was more likely to be caused by an old trauma to the brain.
Dr. House’s team kept the patient awake for twelve hours, but she didn’t have anything resembling a seizure. Dr. House wanted to put the patient under more stress to see if a seizure could be induced, but Dr. Taub reported that the patient was under stress - she had been fighting continuously with her husband who was frustrated she couldn’t remember him, and she kept asking what she did for fun. They had found out before she met her husband, she was a carefree surfer and it appeared she had reverted to that. She started getting serious with her studies several years ago after her brother died in an automobile accident. Dr. House realized (and his own doctor Dr. Nolan confirmed), that Sidney saw her husband as a stranger who was trying to press intimacy on her.
Sidney soon had trouble breathing. They traced this to excess fluid in the lungs. Dr. Hadley thought diabetes insipidus was the most likely cause. The usual cause of diabetes insipidus is damage to the hypothalamus, which explained the incontinence. Dr. House noted the amnesia could be traced to the amygdala and the foot paralysis could be traced to the motor cortex. The most likely reason for all these different areas being affected was spongiform encephalitis. They needed to do surgery to remove part of her brain. This would mean the loss of all her long-term memory.
However, Dr. Taub reported that they couldn’t get the husband’s consent for the surgery, even though the patient wanted the surgery. The husband said that she didn’t know what memories were being lost. Dr. House explained that if they didn’t operate, the prion infection would continue to spread and she would die. The husband felt there had to be another option. However, Dr. House noted that Sidney had developed an arrythmia, which meant the infection had spread to the brain stem and was inoperable. Dr. House ordered the installation of a pacemaker along with chemotherapy and radiation treatment. He informed Sidney and her husband that her prognosis was death within two weeks, but there was a chance she could regain some of her memory during that time.
However, as they were using the flouroscope to place the pacemaker, Dr. Taub noted the patient had rapidly progressive dilating cardiomyopathy. This ruled out spongiform encephalitis and pointed to a systemic disease that was affecting her entire body. They tried to stabilize her heart, but she was suffering from tachycardia and high blood pressure. Dr. Hadley thought it might be endocarditis - an infection in her heart throwing clots that affected her brain. Dr. Chase surmised that her exercising suppressed her immune system, allowing the infection to spread. Dr. House thought it might be an old infection that reasserted itself. Tuberculosis was the most likely candidate. He ordered the multi-antibiotic regimen for it. Dr. Taub reminded him that if it was tuberculosis, the drugs would take time to work and that Sidney might die before they became effective if they didn’t take other interventions. Dr. House ordered them to give her the first dose directly to the lungs in the operating room. After that, they should put her in an isolation room with ultraviolet light and test all the personnel who had contact with her.
On the way to the isolation room, Dr. Chase used his stethoscope and her lungs sounded as if they were filling with fluid. Her oxygen stats were dropping as well. Dr. House returned to the hospital. Dr. Foreman planned to administer intravenous furosemide. However, as she passed under the ultraviolet lights, Dr. House noted something on her ankle. It turned out to be a tattoo that she had tried to have removed. The top layer of skin had been removed, but there was still ink in the lower layers. It turned out she was allergic to the ink and her ultra-marathon running instead over stimulated her immune system, causing a severe allergic reaction. After a full-thickness skin graft, her symptoms improved, although her memory didn’t return right away. On Dr. House’s advice, the husband started treating her as if they had just met and their relationship soon improved.