A young housewife, who happens to be taking some fertility medication, is brought to the hospital when she begins having muscle spasms so bad that she crashes her car. As Margo's symptoms continue to get worse, House and the team think she might have Huntington's Disease but when Margo descends into paranoia, they dig deeper and discover that she might not be telling them the whole truth. Meanwhile, after House and Stacy return from Baltimore with a rekindled relationship, Wilson begins to worry that House is just setting himself up for a hard fall. Also, Cameron is refusing to find out the results of her HIV test.