改编自扬子江事件，二战结束后紫石英号被编入英国远东舰队，驻扎香港。1949年4月20日，紫石英号在此之前我国已经发布渡江战役公告，令各国船只撤离长江。收到解放军的通知后，美国等几个国家相继撤离，只有英国紫石英号满不在乎地以为这只是解放军的口头警告，并不想撤离反而想逆流而上，意图挑衅从中获取利益，从而引出的突围故事。

While sailing lawfully up the Yangste in 1949, the British warship Amethyst found its return to the open sea blocked by Communist Chinese shore batteries that unexpectedly opened fire. In charge, Lietenant Commander Kerans was not however prepared for his crew and his ship to remain as a hostage for the Chinese to use as an international pawn.

En 1949, pendant la guerre civile chinoise, navire de guerre britannique HMS Amethyst navigue jusqu'à la rivière Yangtse, mais sur le voyage de retour trouve son chemin bloqué par un tir de barrage des batteries côtières chinoises communistes.

Die britische Fregatte "Amethyst" gerät im April 1949 zwischen die Fronten des chinesischen Bürgerkriegs. Der Kapitän wagt den Durchbruch des schwer angeschlagenen Schiffs nach Nanking...

Il lungometraggio narra in maniera romanzesca, ma obiettiva un fatto vero accaduto nel 1949 durante la guerra civile in Cina. Al centro della vicenda è un incrociatore inglese che naviga sullo Yangtse per raggiungere Nanchino e portare soccorso ad una colonia di connazionali