Hidden Expedition: Devil's Triangle is the fourth entry in the hidden object game series produced by Big Fish Games since 2006. As in most recent titles of the genre, the adventure elements are more pronounced with full inventory and puzzles complementing the simple hidden object scenes. Like in most first-person point-and-click adventures, the player navigates through various locations by clicking on hotspots positioned over obvious exit openings, like doors and other places. The rooms are presented as a series of static screens with interactive portions. The cursor is context-sensitive, changing shape when hovering over an interactive part of the scenery. It morphs into an eye when over a place with a close-up view, that sometimes contains a hidden object scene or a mini-game. It transforms into golden arrows when over one of the exit hotspots. It becomes a hand when over a scenery object that can be collected. It displays swirling blue circles over special areas where an inventory item can be used.

A scientific organization called H. E. A. T. (Hidden Expedition Adventure Team) sends the experimental submarine Sea-Hawk, powered by a revolutionary device called Bio-Coil, to the famous Bermuda Triangle in search of a lost pilot. As the submarine approaches the mysterious region, pirates suddenly appear and start to board the vessel to steal the precious power source. The crew is forced to evacuate on emergency escape pods, landing on the beach of a strange island with exotic buildings and bizarre inhabitants.