In1861,whentheAmericanCivilWarbrokeout,BelleBoydwasonly17.ShesawUnionsoldierslootinghousesinherhometownofMartinsburg,andshotonetipsysoldierdead.
SoonBoydwasridingallovertheShenandoahValleygatheringinformationfortheConfederacy.Oneday,shelearnedthatUnionsoldiersplannedtoburnatown'sbridgesastheyfled.DashingpastUnionpicketsanddodgingtheirriflefire,shespedtoGeneralStonewallJackson,whotookthebridgesbeforetheycouldbedestroyed.Oftenarrested,Boydwasjustasoftenreleased.Onherlastmissionin1864,shewascarryingletterstoagentsinEnglandwhenhershipwasseizedbyaUnionwarship.Onceagainhercharmdidnotfailher.TheUnioncommanderaskedhertomarryhim.Shewasnotyet20yearsold.
一八六一年，美國南北戰爭爆發，當時貝爾．博伊德才十七歲，住在馬丁斯堡，見北軍四處入屋搶掠，就槍殺了一個醉酒軍人。
她騎着馬，往來謝南多厄河谷各地，為南部邦聯蒐集情報，有一天，聽到北軍敗逃之前，準備燒掉某市的橋梁，就冒着步槍子彈，一面躲閃，一面衝過北軍哨站，趕去通知石牆．傑克遜將軍。傑克遜於是在北軍毀橋之前，佔領了橋梁。博伊德多次被捕，但也多次獲釋。一八六四年，她執行最後一個任務：送信給在英國的特工。但她的船遭北軍戰艦截獲。博伊德的魅力再一次奏效：戰艦指揮官向她求婚。那時她還未滿二十歲。