Like many in Greek mythology, Acrisius punishes his daughter in an attempt to avoid his own fate. Of course, he will not be able to do so.
It was foretold that Acrisius would be killed by the son born to his daughter. To avoid this prophecy, Acrisius kept Danae locked up in a room so no one would fall in love with her.
Zeus still fell in love with her, and entered her room as a shower of gold. When she became pregnant, he was afraid the child would one day murder him, so he locked them in a chest and set them out to sea. They survived, and one day Perseus returned and killed Acrisius, just as foretold by the prophecy.
