Once again, Luke is called to the penitentiary, though for once the Daltons haven't escaped. They have, however, just learned that their cousin Emmett, last survivor of the original Dalton gang, has a son - and that Averell was chosen as his godfather! Now Lucky Luke has to accompany the dumbest bandits in the West to the young boy's house, as Averell has been temporarily entrusted with his education. A job that his brothers see as an excellent opportunity to get rich...