Danae was the only child of Akrisius, king of Argos.
Acrisius had received an oracle, according to which his grandson would kill him.
So he decided to lock up Danae in an underground prison where little light was coming from a small skylight.
From this small skylight the glimpse of Jupiter spotted Danae and he fell deeply in love with her.
In order to enter the prison, he was transformed into golden rain and penetrated.
From their union Perseus was born, the grandson of Akrisius.