In1876,JohnnyJameson(DanDailey),a"drummer"(tr*elingsale*an),istheonlypassengerontheinauguralrunoftheTomahawkandWesternRailroad'snarrowgaugetrainthroughtheColoradoRockies.Duringtheride,theconductortellsJohnnythatcertainpeople,stagecoachoperatorsforexample,wouldliketoseetherailroad'sfranchisefail.Soonafterwards,Dakota(RoryCalhoun),TrancasandGila,whoworkforColonelDawson,theareastagelineoperator,causeagiantbouldertofalldirectlyinthepathofthetrain.EngineerTerenceSweeny(WalterBrennan)managestostopthetrainintime,andheandthecrewthendisembarktomovetherock.JohnnydecidestowalktothetownofEpitaphandhitchesaridewithTrancasandGila.Atthesheriff'soffice,whenJohnnytriestoreportthetrain'sdelaytodeputyChuckityJones(CharlesKemper),heisknockedoutbyTrancas.U.S.MarshalKitDodge,meanwhile,isintheroomnextdoorgettingreadytowelcomethetrainwithhelpfromhistomboyish,knife-wieldinggranddaughterKit(AnneBaxter).Astheyle*eforthedepottheyaresurprisedbyTrancasandGila.ThemarshalshootsTranca*utiswoundedbyGila.JohnnycomesroundandKitsuspectsthathemayalsobeoneofthegang.DespiteChuckityinterveningonhi*ehalfsheordershimtole*etownbeforesunset.KitisdeputizedasaU.S.Marshalbyhergrandfather,whonowcannottr*elbecauseofhiswound.SheandanIndiancompanionnamedPawnee(ChiefYowlachie)areassignedtoescortthetraintoTomahawk.ColonelDawsonordersDakotatojointhepossethatisescortingthetrainandalsoanIndianscout,BlackWolf,tostirupthelocalArapahos.Othergangmembersplottoblowuptheengineduringanightstop.Onlyafterheha*oughthisticketoutoftowndoesSweenylearnthatthereisnotracklaidforthenextfortymiles.Heisinformedbylocalrailwayentrepreneur,Bishop,thattherailswerelostatseaenroutefromEngland.BishopexplainsthatasthetrainmustreachTomahawktofulfilltherequirementsofthefranchisecontract,hehasarrangedfortheenginecartobehauledbyateamofmules.AnotherconditionisthatthetrainmustreachTomahawkbyarapidlyapproachingdeadlinewithatleastonepayingpassenger.KitisnotpleasedtodiscoverthatthepassengerassignedtohercareisSweeny.Johnny,nowreluctanttotr*elonthetrain,isropedalongsidethecabasthelocomotive,minusitspassengercar,setsoffpulledbythemulesandaccompaniedbyassortedwagons.ChineselaundrymanLongTime(VictorSenYung)joinsthegroupwithmuchdelayedlaundryforTomahawk,togetherwithMadameAdelaide(ConnieGilchrist)andherdancinggirls,Annie,Ruby,Clara(MarilynMonroe)andJulie.Amusicianwithpionolaaccompaniesthem.Asplanned,Dawson'*enBat,CharleyandFargoshowupatanightstopclaimingtobetelegraphmenwhoaretheretorepairlinescutbytheArapahosandKitgivesthempermissiontobunkinthecamp.GraduallyKitsoftensherattitudetowardsJohnny.Whenallareasleep,BatandCharleyle*ewhileFargotossessticksofdynamiteundertheengine.Johnny,sleepingalongsidethetrain,*ellsthelitfuseandalertstheothers.KitthencutsthefusewithashotanddisablesFargobutbeforehecantalkDakotakillshim.Sometimelater,afewmile*eyondwherethetrackrestarts,BatandCharleyareplacingdynamitechargesonatrestlebridge.Johhny,KitandPawneearescoutingaheadandstopatthebridge.BatandCharleyconsidershootingthembutarethenthemselvesattackedandkilledbyIndiansandthedynamiteissetoffprematurely.Kit,JohnnyandPawneearechasedbacktothetrainwhichisthenattackedbythewarparty.JohnnyidentifiestheArapahochief,CrookedKnife,h*ingpreviouslyworkedwithhiminatr*ellingwesternshow.Afterthewarpartyisdrivenoff,Johnnyvolunteerstotalkpeacewithhim.HehaslearnedthatLongTimeiscarryingaloadoffireworksanddevelopsaplan.HeiswelcomedbyCrookedKnife,whoagreestoallowthetrainsafepassage.However,someofthebr*esdistrustJohnnyandaskhimtoproduceasignthatheis"bigmedicine."Johnnysetsoffarocket,signalingKitandDakotatosetofftherestofthefireworksonanearbyhill,andtheIndiansareimpressed.Astherailwaybridgeisnowout,Kitintendstotakethethirty-three-tonlocomotiveoveramountainbydi*antlingitandcarryingitinsections.Dawson,meanwhile,thinksheha*eendouble-crossedandshootsBlackWolf.Hethenroundsuphi*enforafinalshowdown.AfterKitdiscoversthatDakotahassabotaged*italwatertower,Dakotajumpsaboardthetrain,slugsJohnnyandatgunpointmakesthefiremanstarttheenginerollingandtakesoffathighspeeddownthetracks.KitjumpsintothecabinbutisknockedoutbyDakota.JohnnyrevivesandwhileheandDakotafightontopofthecabin,KitcomesroundandthrowsherknifeatDakota,causinghimtofallintoar*ine.Dawsonandhisgangthenambushthetrainbutcannotcatchupwithit.However,theymanagetoshootuptheboilerandthetrainslowstoahaltwithinsightofTomahawk.Aposse,headedbyMarshallDodge,ridesoutfromthetownand,togetherwiththeAraphoe,subdueDawson'sgang.Dawsonflee*utispursuedbyPawneewhothrowsatomahawkathimwhichhitshomeoffcamera.Asthetrainhasstoppedjustshortofitsgoal,JohnnytalksthemayorofTomahawkintoextendingthetownlimits,therebyfulfillingtherequirementsofthefranchise.Hedoesso,withsecondstospare.BynowKithasfalleninlovewithJohnnybuthesayshecannotbewithherashecouldnotgiveuphistr*ellinglife.Shegrabsherknifeandthreatenstocripplehimtostophiswanderingways.InthenextsceneitbecomesapparentthatJohnnyisnowworkingasatrainconductor.Asthetrainsetsoffhequicklylimpsafterit,w*ingtohiswife,Kit,andtheirfiveyoungdaughters...