Lamb,basedonthenovelbyBonnieNadzam,tracestheself-discoveryofDavidLambintheweeksfollowingthedisintegrationofhismarriageandthedeathofhisfather.Hopingtoregainsomefaithinhisowngoodness,heturnshisattentiontoTommie,anawkwardandunpopulareleven-year-oldgirl.Lambisconvincedthathecanhelpheravoidadestinyofapathyandemptiness,andtakesTommieforaroadtripfromChicagototheRockies,planningtoinitiateherintothebeautyofthemountainwilderness.Thejourneyshakestheminwaysneitherexpects.