Back from a secret mission in Mexico, Lucky Luke discovers that a new hero has conquered the West. Allan Pinkerton, a fan of revolutionary investigative methods and zero tolerance, wants to push the lonely vigilante towards retirement in order to win the favors of President Lincoln. Daniel Pennac and Tonino Ben acquista sign with four hands an exceptional Lucky Luke on which blows the spirit of the great Goscinny, a subtle western for young and old, beautifully staged by Achdé.