Theseus wanted to stop his father from killing innocent people with the minotaur(half man half bull). so he volunteered to kill the minotaur.
The minotaur was kept in the labyrinth. which was a maze that Theseus had to go through in order to kill the minotaur. Theseus fell in love with a girl that found out he was going to kill the Minotaur. So she gave him a ball of yarn to track his way through the labyrinth.
Theseus defeated the Minotaur. After he sailed away without his girl. He forgot to change his sails to white which his father thought he died because if he didn't it meant he died. So his father jumped of a cliff from depression. The end.