When Susan (Eva Green), an epidemiologist, reemerges from an affair gone sour, she encounters a peculiar patient—a Glasgow truck driver who experienced a sudden, uncontrollable crying fit. Now he is calm, but he has lost his sense of smell. Susan learns there are 11 cases like him in Glasgow, 7 in Aberdeen, 5 in Dundee, and 18 in Edinburgh. In fact, Great Britain has 100 cases, with additional ones reported in France, Belgium, Italy, and Spain, and they all appeared in the last 24 hours. Although Susan's encounter with Michael (Ewan McGregor), a local restaurant chef, holds the promise of new love, the world is about to change dramatically. People across the globe begin to suffer strange symptoms, affecting the emotions, then the senses.