Great idea! We've already got a very detailed walkthrough written by players, but I think a small summary will leave more room for exploration:
First, gather as many chests as you can around the house, check the guy under the bridge to get a necklace, steal all the bread to get enough money to buy a sword and other items >>> Head into the forest >>> Meet Kay who is poisoned >>> go see the centaur Chiron for the antidote >>> return to cure Kay, receive a pass to enter Grailwood village >>> talk to Percival to get the key left by Lancelot's father (there's a side quest with Lebius here) >>> go back home to open the basement >>> take Excalibur's remains to the purple barrier near the house >>> enter the ruins to get the gem of Excalibur and the magic key >>> enter the graveyard to save Arthur (you can do Gawain's quest beforehand) >>> go to Asher's house to get the recommendation letter >>> enter Merlin's crypt and uncover the final secret.