Black Circle is the sixth Carol Reed game. Like the previous titles in the Carol Reed series, the game is a point and click adventure set in Norrköping, Sweden. It's created with real photographs with a watercolour effect. Carol is a British girl but she lives in Sweden, where she has taken over a detective agency. In Black Circle, Carol is contacted by her neighbour Oscar, who is a retired doctor. On one of his morning walks he discovers a body, but when he goes home to call the police the body disappears and the police don't believe him. He asks Carol to help him find out what happened. Carol travels around town, finding clues, talking to people and solving puzzles.
Each photograph is a node and can be exited using arrows on the screen. Several nodes form a location. Travelling from location to location is accomplished by the use of a map.
The notebook gives access to an in-game hint system. The game is fully voiced (in English) and has optional subtitles.