The life and career of forgotten Welsh veterinary surgeon, medic and adventurer Griffith Evans, who discovered that blood parasites cause disease and met Abraham Lincoln and Ulysses S. Grant. In 1880, Welsh army veterinary surgeon Griffith Evans made the groundbreaking discovery that blood parasites, then universally considered benign, were pathogenic. This was a crucial milestone in the battle against parasitic diseases in animals and humans, but Evans was spurned by his peers and colleagues. His conclusions from experiments with diseased horses were acknowledged by Koch and Pasteur, but it took many years before his achievement received general recognition. Long ignored and forgotten, restoring Evans to his rightful eminence is important for the history of veterinary and medical science in general, and Welsh science in particular. Evans's talent for engagement with people and cultures characterized his life in Canada and India. During a long and productive retirement in north Wales, he immersed himself in local and national affairs. At his centenary in 1935, Evans received the accolades of his profession, community, and family, dying peacefully in his hundredth year. Since that time, his name has faded into obscurity.