Theseus is enjoying his place as hero, prince, and heir to the throne of Athens.
Call to Adventure
The young hero finds out that every few years, young Athenians must be sent off to the island of Crete to be sacrificed to the man-eating Minotaur, who lives in an inescapable Labyrinth.
Refusal of the Call
Theseus doesn't refuse the call at all. He jumps at the chance for adventure.
Meeting of the Mentor
Theseus convinces his father, King Aegeus, to let him go. Unlike a lot of mentors, King Aegeus doesn't really give Theseus any advice to help him along the way, and he doesn't even encourage his son to go on the dangerous voyage.
Crossing the Threshold
Despite his father's reservations, Theseus hops on the boat to Crete determined to slay the Minotaur and save the young people marked for human sacrifice. He promises Aegeus that he'll change the black sail of the ship to white on his return to Athens to show his father that he made it back alive.
Tests, Allies, Enemies
Theseus makes a great ally in the Cretan Princess Ariadne. The beautiful maiden falls in love with him and tells him how to escape the Labyrinth by trailing string behind him.
Approach to the Inmost Cave
Theseus prepares to enter the Labyrinth and battle the Minotaur.
Theseus fights the ferocious Minotaur and defeats him.
Reward (Seizing the Sword)
The young hero takes the Princess Ariadne with him as he sails back to Greece with the young Athenians.
The Road Back
For some reason, Theseus decides to abandon the Princess Ariadne on an island on the way back to Greece. Unlike a lot of heroes, who become better people over the course of an adventure, Theseus becomes more of a jerk.
This section of the story veers away from Vogler's formula. Theseus is so busy thinking about how awesome he is that he forgets to change the sail to white. When Aegeus sees the black-sailed ship approaching Athens, he thinks Theseus is dead and kills himself. So, Theseus doesn't face another obstacle from which he barely emerges alive. Instead, he actually causes the death of his own father.
Return with the Elixir
Theseus is now a totally famous hero, because of his defeat of the Minotaur. Because of his father's death, he's also the King of Athens. Theseus's reward is bittersweet, since it was accomplished (literally) over his father's dead body.