Board Thread:General Discussion/@comment-3010035-20150413083321

Well in Heart of Gold, they mentioned Midas was passing by, and Robin also realises he wants to be a theif again in the same episode "Stealing from the rich and giving to the poor."

Well Frederick was killed when he protected Midas from theives, so maybe it was Robin Hood and his Merry Men who ambushed Midas.

I don't think this theory would have a huge effect on the show, it's just a cool little knot to tie. 