Danae and Perseus were put into a underground shack by her father, King Acrisius. He sent them away from the world, underground into a bronze shack. He did this because he was told that his grandchild was destined to kill and because Danae had a child.
Danae begged her father not to throw her and her child in a sealed box and Perseus were thrown into the ocean in a box into the ocean. He heard her cries but he threw Danae and Perseus into the water anyway. King Acrisuis showed no mercy.
The call to adventure
Meeting with the mentor
Polydectes sent Perseus to bring him the head of Medusa. He sent him knowing he wouldn't come back, it was basically impossible for one man to defeat Medusa. He wanted Perseus to die for he could marry his mother, Danae.
Perseus was reluctant by his bold promise he made to Polydectus. He knew that it was impossible for one man alone to bare the head of Medusa. But he pushed through and went on the journey anyway's.