CowboyJamesFranciscusseeksfameandfortunebycapturingaTyrannosaurusRexlivingintheForbiddenValleyandputtingitinaMexicancircus.Hisvictim,calledtheGwangi,turnsouttohaveanaversiontobeingshowninpublic.Anotherfilmfeaturingthestop-actionspecialeffectstalentsofRayHarryhausen.