Lucky Luke TPB Volume 49 Daltons Amnesia

"After a fellow inmate, having received a blow to the head, forgets his own name and is freed as a brand new man, the Daltons start pretending to be amnesiac in order to escape the prison. So as to test their supposed amnesia - and hopefully allow them to retrieve their memories should it be real - they are put in familiar situations: bank hold-ups, train robberies... under Lucky Luke's supervision, of course!"