My friend Link went to the future and Ganon had taken over the land to bring it to an era of darkness with the Triforce.  Meanwhile in the present, Ganon is in your castle pretending to be an ally.  However he is actually very evil so he should probably be deported back to the Gerudo Valley before his actions cause a bunch of alternate timelines or something.  Look at his face, he's clearly a bad guy.  If you are wondering about the credibility of Link's story about time travel, here this out: he had an ocarina.  That's some legit stuff right there.