US Cavalry Colonel Oswald has orders to test fat Bertha, the White House's top-secret artillery pet project. Alas he looses control over it after the Daltons saw it, so they escape to get hold of it, but so want Indian chief Oochi Coochie and the now dismounted troopers. Lucky must arrest the Daltons again at risk of being bombed to Kingdom come, and the Colonel gets a surprise visit.
