King Graham and Queen Valanice had two children, Alexander and Rosella, and the kingdom was once peaceful. It wasn't long until Alexander was snatched from his crib and things started to take a turn for the worse. A three-headed dragon threatens the ever-peaceful Daventry, and requires a maiden to be sacrificed every year. Rosella is the chosen one.
Meanwhile, in a secluded house atop a mountain in the land of Llewdor, the evil wizard called Manannan keeps a young lad named Gwydion as his slave, forcing him to do menial tasks as he prepares his spells and observes the country through his telescope. Gwydion must find a way to outsmart the wizard, escape, and eventually discover the truth about his own identity.
King's Quest III: To Heir is Human is an action and adventure game where you play as Gwydion, navigating through interconnected screens with arrow keys and interacting with the environment by typing verb and noun combination commands. You also have a magic map that allows you to teleport to different areas. The gameplay gets more challenging with new items to collect and complex actions required to execute, raising the difficulty level. A significant part of the game takes place in real time, with Manannan following his own schedule, forcing you to plan and time your actions carefully. There is also a time limit on the first major quest.