Set in the 1930s, “Fortress Besieged” follows the misadventures of Fang Hung-chien, a bumbling everyman who wastes his time studying abroad, and secures a fake degree when learning he has run out of money and must return home to China. Fang was the son of a country gentleman. A marriage had been arranged for him while at university, but the intended wife died before he could see her.

抗战初期，外国留学生方鸿渐（陈道明饰）回到了祖国。方鸿渐其实是在国外混了几年，一个学位没取得，最后没法才买了个学位归国的。出身封建家庭的鸿渐家里早给他订了亲，只是未婚妻没来得及和他结婚就逝世了。鸿渐回国后一直居住在丈人的家里，丈人颇有些能耐，为他谋了一份不错的职业。女博士苏文纨一直对鸿渐有好感，而鸿渐迷恋的却是在苏小姐家里第一次拜访认识的唐小姐。随后，鸿渐与唐小姐渐渐打得火热，然而丈人家看出了他和唐小姐的往来，渐渐冷落了他，而后鸿渐和唐小姐亦因误会而结束。 失恋后的鸿渐和当时同样追求苏小姐失败的留学生赵辛楣（英达饰）成了莫逆，二人同时受到了内地的三闾大学的聘请。于是两位好友一起上路了，前往三闾大学去开展他们的新生活。