Andy Lau stars as Zhao Zilong, a veteran general of the Kingdom of Shu who took a last stand against the invading forces from the Kingdom of Wei. Maggie Q is the fictional Cao Ying, a grand-daughter of the warlord Cao Cao, whose son Cao Pi became the first emperor of the Kingdom of Wei.
The story depicts an alternate history, following the events that unfolded in the Three Kingdoms era through the life of the legendary Shu general Zhao Zilong. Zhao Zilong began his military career as a soldier in Liu Bei's army. Zhao Zilong once displayed his fine spear skills to Liu Bei in a small face-off with Guan Yu and Zhang Fei. This impressed Liu Bei, and he decided to promote Zhao Zilong to the rank of a general. Zhao Zilong was bestowed with the 'All Piercing Spear'.
Zhao Zilong scored his first victory in battle by outwitting Cao Cao at the Battle of Changban. He managed to rescue Liu Bei's son, A Dou from the clutches of the forces of Cao Cao by fighting them single-handedly. Cao Cao's life was put in great peril and he also lost his personal weapon to Zhao Zilong. Cao Ying, who had witnessed Zhao Zilong's acts, swore to help her grandfather regain his lost pride by capturing Zhao Zilong alive.
As history passed, Zhao Zilong had never lost in any battle he fought in, hence earning himself the title of 'The Undefeated General'(長勝將軍). Cao Pi forced the last ruling Han emperor to abdicate in his favour and proclaimed himself Emperor of the Kingdom of Wei. Thereafter, Liu Bei assumed the title of Emperor of Shu-Han as a spiritual successor to the fallen Han dynasty by carrying on the family name. Zhao Zilong joined the ranks of Guan Yu, Zhang Fei, Ma Chao and Huang Zhong to be one of the Five Tiger Generals sworn to defend the Han imperial family.
Years after Zhuge Liang's first failed Northern Expedition, he embarked on a second expedition. Zhao Zilong had reached the age of 71 by then, hence Zhuge Liang had doubts about allowing him to join in the expedition. However his persistence ensured him a role in the expedition. The Chancellor handed him two satches, instructing him to open them as per situations. Zhao Zilong set forth on the expedition expecting to achieve a major victory once more. His first feat was the slaying of the four sons of Wei general Han Xin. As Han Xin retreated, it became obvious that it was a ploy to lure Zhao Zilong into a trap, planned by the Wei commander Cao Ying. Zhao Zilong was forced to retreat to the Yellowbird Peak. It was there where Zhao Zilong pitted his last strength against Cao Ying.
In a single one-to-one duel, Zhao Zilong bouted Cao Ying but decided to let her off. During the fight, the undefeated general received a battle scar for the first time ever in his career. The surbordinate generals of Zhao Zilong engaged in a fierce battle with the Wei forces, but were defeated after Cao Ying sacrificed Han Xin to bring gunpowder into the battlefield. All was lost for Zhao Zilong. He stripped off his armour, picked up his Piercing Spear, and charged towards the Wei forces in a last ditch effort, swearing to defend the Yellowbird Peak, and the dignity of the Kingdom of Shu-Han with the last general and last man.
年过古稀的赵云(刘德华饰)为了帮刘备踏平魏吴再度出山，却在凤鸣山上被困，迎来人生中的终极决战。回思往事立残阳，在这电光火石中，一幕幕征战中的腥风血雨，一阵阵军旅间的喜笑悲愁，纷纷出现在这老将军的眼前。
三国乱世，魏军强势压境，初任工兵的赵云遇上抱打不平的同乡兄长罗平安(洪金宝饰)，两人一见如顾，互诉对乱世的一片憧憬。在蜀国军师诸葛亮(濮存昕饰)以攻为守的策略下，主动请缨劫寨扰敌立下大功。长板坡一役，为免罗平安遗失刘备妻儿的死罪，赵云单枪匹马杀入曹营救回幼主，从而一战成名。
因“单骑救主”有功，赵云被委以重任与蜀国上将黄忠老将军一起出征定军山，此役是蜀国收取汉中奠下蜀国基业的重要一仗。不料黄忠为争头功在罗平安的鼓动下提前出兵，却不想中了曹操的奸计伤亡惨重，危难时刻赵云及时赶到义救黄忠和罗平安，并在诸葛亮的妙计下烧掉曹军粮草再立大功。赵云荣升为五虎大将，而此时的罗平安却是心中百味。
时间如梭，五虎大将的关、张、马、黄都先后辞世，两鬓斑白的诸葛亮再一次策动歼灭曹魏大计，不服老的赵云坚持要做先锋大将。不料此次的劲敌竟是曹操的孙女曹婴(Maggie Q饰)，这个美得像雪一般的少女，弓马娴熟，智勇双全，带着10万大军欲生擒赵云以了祖父心愿。而对赵子龙爱恨交织的罗平安却在最后一刻作出了一个令他后悔莫及的决定--他把赵云最后一次出征的军机出卖给了曹婴。
而足智多谋的诸葛亮也把赵云当成诱敌之傀儡，寄望曹婴和赵云的大战，能让他暗渡陈仓，用全军在三个时辰里攻下魏之主城六郡。此次此刻，赵云该何去何从。
