I find the Epic of Gilgamesh to be an intriguing (not to mention ancient) story about a very dynamic character who goes looking for the secrets of life for himself only to find the secrets of life for everything else.
Characters: Gilgamesh is a tyrant of a king who abuses his power and sleeps with every woman he wants (particularly newlyweds.) He seems to be a king who justifies is actions believing that without his input the whole kingdom (possibly the whole world) would fall on its face. It's only through the friendship of the once lowly Enkidu that Gilgamesh learns compassion and gains a greater vision of purpose in his life. Enkidu's death makes Gilgamesh fear his own, prompting him to find the secret to immortality. After journeying to the ends of the earth he fails to become immortal but learns that the world, nature, friendship, and even humanity itself can live on forever. He saw that his kingdom survived without him and the world moves on without any change.
Enkidu is a man amongst nature and friend to the animals, but when he lay with a woman he became a member of human society and lost the animals favor. Enkidu meets Gilgamesh at a wedding. Enkidu fights Gilgamesh in response to his attempt at sleeping with the many brides. As a character, Enkidu seems to represent a purehearted foil to Gilgamesh with a background in the purity of nature. His friendship to Gilgamesh turns the corrupt king into a caring soul.
This is a tale about accepting one's finitude after a futile attempt at surpassing eternity. It's a tale with a lot of resonance (for me anyway.)
The first act would introduce Gilgamesh and Enkidu leading to their first encounter, a fistfight spreading utter chaos in the middle of a wedding. The two become friends and Gilgamesh invites Enkidu on a quest to gain eternal fame by conquering a sacred cedar forest.
Gilgamesh and Enkidu kill the beast guarding the forest. They fight a bull threatening Gilgamesh's kingdom. Enkidu dies leading Gilgamesh to fear that one day he too must die. This causes Gilgamesh to search for Utnapishtim, an immortal man and the ends of the earth to teach him the secret of eternal life.
Gilgamesh journeys and finds Utnaphishtim and learns that there is no way he can become immortal. He returns to his kingdom and sees that even though he had not ruled his kingdom, it still stood just as fine without him.
My idea for a modern adaption of this story is if Gilgamesh was the CEO of a big business. Enkidnu would be his new executive associate and these battles for fame in act two could be Gilgamesh taking over other rival businesses. Gilgamesh would have the fear of losing his company and would still have the motivation to run his business forever.