(Michael Sheen) once had a successful career as an architect and a beautiful wife, Stevie (Anastasia Griffith), but suddenly his life has been thrown into disarray. Mark now finds himself incapable of climbing the stairs without following a carefully planned sequence, he washes his hands constantly, and he curses violently and without provocation at odd intervals. Mark''s firm has put him on suspension, Stevie has given up on Mark, and his friends Nathan (Adrian Bower) and Kathy (Claudie Blakley) are tempted to do the same when a number of diagnoses and treatments from various doctors fail to bring positive results. While waiting to see another specialist, Mark meets Charlotte (Shirley Henderson), a woman who suffers from Obsessive Compulsive Disorder, and she suggests that his malady may be the same as hers. In time, it is determined that Mark has OCD and Tourette''s syndrome, and with the help of a support group he attends with Charlotte, Mark finally finds ways to successfully deal with his problems. But will his progress be fast and thorough enough to please either Stevie or his employers?