宋末蒙古蒙哥大(dà )汗南(nán )下侵宋,途中遇到飞天炮阻击身受(shòu )重伤(shāng )。后法王虽偷得飞天炮,然蒙哥伤势(shì )加重(chóng ),只得撤兵。返程中被忽(hū )必烈偷袭,逃(táo )入雪(xuě )山。蒙哥感到命不久已(yǐ ),写下血书,传(chuán )位尚(shàng )年幼王子海都后自尽(jìn )。大雪山中人(rén )马走(zǒu )散,飞天炮和血书失踪(zōng ),海都逃出雪(xuě )山后遇到受伤的法王,原来(lái )他受(shòu )到中原三大高手的袭击,他们一起(qǐ )返回(huí )雪山找寻其它队伍但是雪山迷宫(gōng )使他(tā )们放弃。与此同时三大(dà )高手也感无(wú )力进(jìn )入雪山,将进雪山迷城(chéng )的地图分成(chéng )三份(fèn )交各人保存。法王带着(zhe )海都勉强到(dào )达师(shī )弟银枪法王处,将海都(dōu )托付给师弟(dì )后毒发身亡。海都从此身负(fù )夺回帝位的重任。