So Charles Lee accidentally had his hands on the Apple. Before using it for world domination or whatnot, like the jealous little bitch he was, he decided to use it against Connor - by making Haytham read Hay/Con fics so that his mentor would be disgusted by his own son, and therefore stop trying to win him over to the Templar cause.
As for pairing, Hay/Con please, though if author!anon finds some one-sided Charles/Haytham necessary, that's fine too :)