If you need the story, there's no solidly known proven way. If you can live in sandbox Fable, open up the user.ini and prefix the
ActivateQuest("Gameflow");
line with // like so:
//ActivateQuest("Gameflow");
And you will spawn as an adult in the middle of Lookout Point, quests disabled so gameflow is broken at the start. I should also mention that you'll start with apprentice clothes, no experience, no weapons, no money, no spells (you would have the lightning spell at least by this point) and be pathetically weak. So this is usually accompanied with a chest spawn for basic gear and start up funds.
Now, there's a theory of doing the previously mentioned and manually activating the wasp quest (open the qst file in levels, find the quest, set it to true), and this would activate the quest, completing the quest could, in theory (an untested theory mind you), switch the flag for other quests and continue the gameflow from that point. But I haven't tried it, so wouldn't know. Do this at your own risk.