I Swear follows the true story of Tourette Syndrome campaigner John Davidson's journey with Tourette's through his troubled teens and early adulthood, having been diagnosed at 15 years old in 1980s Britain - a time when the condition was little known and entirely misunderstood. Initially alienated from his peers and his family, Davidson perseveres in his attempt to live a 'normal' life against the odds, finding some unlikely champions along the way.