The inhabitants of the planet Rhea are being terrorized by a mysterious organization known as Hell Stones. To save his people, the king of Rhea himself steps out of his palace in order to single-handedly avert the threat.

The Scheme is an action game with role-playing and light platforming elements. The player controls the king as he explores vast outdoor and indoor environments. While some locations are simple side-scrolling areas, others are built like large mazes with platforming segments - the king has to jump on platforms to access certain areas or avoid enemy attacks, however, he doesn't take falling damage. Enemies respawn after the protagonist leaves the screen and returns. The king shoots energy orbs at the enemies, their type can be changed and upgraded as the game advances.

The role-playing element is present in levels and character development. Enemies leave two kinds of power-ups upon defeat: life-restoring and force-increasing, the latter being roughly equivalent to experience points. Leveling up occurs after accumulating certain amounts of these power-ups, increasing the main character's hit points. It is often required to level up in order to be able to access areas with harder enemies or defeat bosses.