Woundedandontherun,notoriousgunmanQuirtEvans(JohnWayne)gallopsontoafarmownedbyQuakerThomasWorth(JohnHalloran)andhisfamilyandcollapses.WhenQuirturgentlyinsistsuponsendingatelegram,ThomasandhisdaughterPenelope(GailRussell)drivehimintotownintheirwagon.Afterwiringaclaimtothelandrecorder'soffice,QuirtkissesPennyandthenpassesout.Ignoringthedoctor'sadvicetoridthemselvesofthegunman,thecompassionateWorthfamilytendstothedeliriousQuirt,andPennybecomesintriguedbyhisravingsofpastloves.
　　Quirtrecoveringunderthecareofthetwowomen(fromlefttoright:Rich,Russell,andWayne)
　　Dayslater,whenQuirtregainsconsciousness,Pennypatientlyexplainsthefamily'sbeliefinnon-violence.Threeweekslater,LaredoStevens(BruceCabot)andHondoJeffries(LouisFaust)rideintotownlookingforQuirt.WhenPenny'syoungerbrotherJohnny(StephenGrant)rusheshometoinformQuirtofhisvisitors,Quirtquicklypreparestoflee.Penny,nowsmittenwithQuirt,offerstorunoffwithhim.Atthesoundofapproachinghorses,Quirtgrabshisgunanddiscoversthatithasbeenemptied.Traininghisgunonthedoorway,QuirtcalmlygreetsHondoandLaredo.ThinkingthatQuirthastheupperhand,Laredoofferstobuyhisclaim.WhenQuirtsetsthepriceat$20,000,Laredohandsover$5,000ingoldandchallengeshimtocomeforthebalancewhenheisable–ifhehasthenerve.
　　Afterward,Quirtsaddleshishorse,butwhenPennybegshimtostay,hechangeshismind.Later,QuirtlearnsthatcantankerousrancherFrederickCarson(PaulHurst)hasdammedupthestreamthatrunsthroughthevalley,thusdrainingtheWorths'irrigationditches.QuirtintimidatesCarsonintoopeningthedam.
　　OneSunday,PennyasksQuirttojointhefamilyforaride.Beforetheyleave,MarshalWistfulMcClintock(HarryCarey)comestoquestionQuirtaboutastagecoachrobbery.ThefamilyswearsthatQuirtwaswiththematthetime.ThemarshalthenasksQuirtwhyheresignedasWyattEarp'sdeputy,soldhisranchandcrossedovertothewrongsideofthelawsoonaftercattlemanWaltEnniswasgunneddowninasaloonbrawl.WhenQuirtrefusestoanswer,themarshalleaves.PennythenbegsQuirttosteerclearofLaredo,andheacquiescesbecauseofhisloveforher.
　　AsQuirtandtheWorthsridetotheQuakergathering,Quirt'serstwhilesidekick,RandyMcCall(LeeDixon),tagsalong.RandytellsQuirtthatLaredoplanstorustleaherdofcattleandsuggeststhattheythenstealtheherdfromLaredoandlethimtaketheblame.Mr.WorthgivesQuirtaBibleforendingthefeudwithCarson.FearingthathewillneverbeabletoliveuptoPenny'sexpectations,QuirtabruptlyleaveswithRandy.
　　QuirtandRandystealtheherdfromtheoriginalrustlers.TheythencelebratewithshowgirlsLilaNeal(JoanBarton)andChristineTaylor(RosemaryBertrand).WhenLila,sensingachangeinheroldflame,teasesQuirtabouthisBible,QuirtbecomesangryandridesbacktotheWorthfarm.Overjoyed,Pennythrowsherarmsaroundhim,justasthemarshalarrivestoquestionQuirtabouttherustling.QuirtstatesthatLilacanprovidehimwithanalibi.PennyishurtthatQuirtwaswithhisoldflame,whosheheardhimtalkaboutinhisdelirium,thinkingQuirtprefersLila'sfairhair.QuirtrealizesthedepthofhisfeelingsforPenny,andtheykisshungrilyinthebarn,whilethecamerafades.
　　ThemarshalwarnsQuirtthatheisthewrongmanforPenny.Quirtdecidestoproposetoheranyway.Insteadofreplying,PennyinvitesQuirttojoinherpickingblackberries.QuirtanswersPenny'squestionsabouthisearlylife.KindlyWaltEnnisraisedhimafterhisparentsweremassacredbyIndians.ThenEnniswasmurdered.
　　QuirtandPennyareambushedandchasedbyLaredoandHondoontheirwayhome.Theirwagonplungesoveracliffintotheriver,causingPennytodevelopadangerousfever.WhenthedoctorinformsQuirtthatthereisnohopeforher,Quirtstrapsonhispistolandridesintotowntoexactrevenge.AfterQuirtleaves,Penny'sfeversuddenlybreaks.
　　Intown,QuirtsendsBradleytotellLaredoandHondoheiswaitingfortheminthestreet.Pennyandherfamilyarrive.ShegetsQuirttosurrenderhisguntoher.AsLaredoandHondodrawtheirguns,MarshalMcClintockshootsthemboth.QuirtridesoffinthewagonwithPenny.ThemarshalpicksupQuirt'sdiscardedweapon.BradleycommentsthatQuirtmayneedtheweapon,towhichthemarshalsays,"Onlyamanwhocarriesaguneverneedsone."And,thefilmfadestoblack.