太傅(fù )嫡女沈宛宛与宁国侯世子萧至(zhì )大婚(hūn )在即,萧至的青梅赵茵(yīn )儿将正室(shì )嫁衣(yī )换成妾室粉色嫁衣,当(dāng )众羞辱沈(shěn )家。萧(xiāo )至偏袒赵茵儿,让沈宛(wǎn )宛忍让。沈宛宛不甘受辱,借皇上赐婚(hūn )之机,改嫁给萧至驻守(shǒu )边关的兄(xiōng )长萧(xiāo )宸,助萧宸取而代之成(chéng )为世子。赵(zhào )茵儿(ér )自食恶果沦为姨娘,萧(xiāo )至失势后自甘(gān )堕落,竟勾结二皇子与(yǔ )北狄通敌,暗害萧宸。沈宛宛与萧(xiāo )宸将(jiāng )计就计,大破北狄,揪出(chū )萧至与二(èr )皇子(zǐ )罪证。最终萧至被斩,奸(jiān )人伏法,二人镇(zhèn )守边关,安稳度日。