LongshoremanJohnnyBarnes(BurgessMeredith)isinlovewithKittyTracy(IreneHervey),barmaidatherfather'swaterfrontsaloon,andhebeatsupCassidy(JoeDowning),acrookedpoliticianwhohasbeenannoyingher.CassidyismurderedthatnightandJohnnyisjailedforthecrime.Kitty,herfatherAndyTracy(RaymondWalburn),andwaterfront-priestFatherCameron(RobertArmstrongbelieveJohnnyisinnocentbutallevidencepointstohisguilt.Johnny'sstorythathewasatpiersevenwatchingatugboatbeingrepairedisdiscreditedbythepolice,whoprovethatpiersevenhaslongbeenclosed,andnotugboatsuchastheonedescribedbyJohnnycanbefound.Followingupacluefoundbyherfather,Kittyfindstheboatanduncoverstheidentityoftherealmurderer,AlcatrazescapeeMonteMarch(EdwardPawley).KittyandFatherCameronlocateandconfronthim,buthislovingwifeFrancesMarch(EstherRalston)isreadytodefendhim.