Athens had a debt to settle with King Minos of Crete. This meant that every few years Athens would have to send 7 boys and 7 girls to be sacrificed by the dreaded minotaur.
The time has come once again! Which one of you shall make the honourable sacrifice
Son, I can't let you be ripped apart by the mighty beast!
The King agreed to let Theseus go, but on one condition, he would be given white sails instead of the usual black ones to wield proudly on his return for the King to know he's back.
Father I will not be sacrificed...I will slay treacherous monster!
I'll do it Father! As the Prince of Athens I have a responsibility to my people!
...Hours later, in Crete Princess Ariadne spots Theseus
The princess helps Theseus by giving a sword and a ball of yarn he can use to leave a trail within the maze...
Wow he is so handsome...I can't let him be sacrificed!
To everyone's surprise Theseus defeated the beast and freed everyone...on his way back home he brought the Princess with him...
Unfortunately for Ariadne, Theseus turns out to be kind of a jerk who ditches her on the island of Naxos. Due to sheer happiness Theseus forgets to put up the white sails like he promised his father.
We must part ways...
Meanwhile, on nearby ledge the King spots a sailboat approaching the kingdom, however, the boat held black sails, meaning the death of his child. This caused the King to jump off the ledge, killing him. When Theseus arrived he obtained the thrown along with all the fame and glory...but at what price?