宋末蒙古(gǔ )蒙哥大汗南(nán )下侵宋,途中遇到飞天炮阻(zǔ )击身受重伤(shāng )。后法王虽偷得飞天炮,然蒙(méng )哥伤势加重(chóng ),只得撤兵。返程中被忽必烈(liè )偷袭,逃入雪(xuě )山。蒙哥感到命不久已,写下(xià )血书,传位尚(shàng )年幼王子海都(dōu )后自尽。大雪(xuě )山中人马走(zǒu )散,飞天炮和血(xuè )书失踪,海都(dōu )逃出雪山后(hòu )遇到受伤的法(fǎ )王,原来他受(shòu )到中原三大高手的袭击,他(tā )们一起返回(huí )雪山找寻其它队伍但是雪(xuě )山迷宫使他(tā )们放弃。与此同时三大高手(shǒu )也感无力进(jìn )入雪山,将进雪山迷城的地(dì )图分成三份(fèn )交各人保存。法(fǎ )王带着海都(dōu )勉强到达师(shī )弟银枪法王处(chù ),将海都托付(fù )给师弟后毒(dú )发身亡。海都从(cóng )此身负夺回(huí )帝位的重任(rèn )。