A general amnesty puts the Daltons back on the streets, something Lucky Luke isn't happy about. And, to make it worse, they seem to have become model citizens. It's all an act, though, and it doesn't take long for the stupidest quartet in the West to be back behind bars. Luke is already riding off into the sunset... But he's not counting on a riled-up Apache tribe that attacks the penitentiary where the Daltons are locked up...