Rojrat, the owner of a well-known jewelry mansion, is holding an exclusive jewelry show for his VIP guests in a luxury hotel of private island. The highlight of the show is to exhibit the gorgeous “The Blue Ocean Diamond” that had been collected for years. Because of its pricelessness, Prompoom an ex-policeman is hired for security tasks by Lapin, Rojrat's trusted secretary. Prompoom is delighted to get this job not only because of high wage but also of the chance to arrest Baramee, an influential businessman who caused his father's death.

This job leads Promphoom to meet and stay near Lalisa, Rojrat’s daughter and the model who presents the Ocean Diamond necklace. He likes her but unfortunately she has just returned from abroad with her boyfriend Jeffrey, a Michelin-star chef. Unexpectedly the Ocean Diamond was missing and Prompoom needs to find the robber among these VIP guests. So begins the investigation story and unexpected fancy between Promphoom and Lalisa, along with the disclosure of unexpected truth!