A huge multi-headed amphibious sea monster attacked the cruise ship, eating most of the tourists on board (including the captain) and only a few survivors survived. When John and others arrived, the Argo was in a pool of blood ... Only a few survivors were left on board, including Cui Lin and Simon, the engineer who built the Argo. It was then that Finnegan understood the task of mercenaries. Their task was to rob the luxury ship, and if they failed, they would blow it up.

At first, John didn't believe that the "Argo" told by the survivor was devastated by the so-called "deep-sea devil". It was not until he found that the crew and mercenaries died one after another that he realized that he had been put in a dangerous situation of narrow escape. In desperate circumstances, he can only join hands with Cui Lin and mercenaries to deal with the bloodthirsty "deep-sea devil".