There is no scientific theory by the name of Charles theories. However, there is a scientist named Jacques Charles, who proposed the Charles' law or the law of volumes. This law describes the relationship between the volume and temperature of a gas, stating that the volume of a gas is directly proportional to its temperature when pressure is held constant.
On the other hand, Robert Louis Stevenson's novel "Strange Case of Dr. Jekyll and Mr. Hyde" introduces the concept of dual personality and moral duality, not related to any scientific theories.