It seems that the relationship between Tex Murphy, the private investigator in post-apocalyptic San Francisco, and his sweetheart Chelsee finally entered a happy phase. Tex is going on a date with Chelsee, they talk about their feelings and their future, and Chelsee asks Tex to tell her the story of his first case as a PI. This is where the player begins the game - as young Tex, still an idealist, full of energy and with none of the ironic bitterness of his later years.
A beautiful girl enters his office. Her name is Sylvia Linsky, and she asks him to investigate a case. Her father, Carl Linsky, has apparently committed suicide. But although there seems to be nothing suspicious in the circumstances of his death, Sylvia tells Tex she is convinced it was a murder. Tex's first investigation, which will influence his entire life, is about to begin.
The general storyline of Overseer is similar to that of Mean Streets, the first game in Tex Murphy series, but it is told in a much more detailed way; gameplay style and locations are for the most part completely different. The gameplay system is similar to the one first implemented in Under a Killing Moon. The player can move around in a fully 3D environment, which can be viewed from different positions and angles at any time. Dialogues and cutscenes feature live actors. There are a number of puzzles to solve in Overseer, but in-game help is available if players find them too difficult.