1) A fisherman catches a magical fish that grants him wealth but turns him into marble when he enters the forbidden No Return Castle. 
2) His twin sons go on adventures; one frees the king's daughter from a snake and marries her, but enters the castle and is turned to marble. 
3) The other son rescues his twin brother and the magical items with an unguent, breaking the castle's curse. They return home with the first son's new wife.