I have completed the forest to find the cure, the village dragon skin exchange key quest, and now to enter the dungeon need to find Sir Arthur's letter, indicating that Arthur's house is near the cemetery, but can not find;

And will the game have a walkthrough?

After getting Ban's key from Percival, you'll need to go back to Lancelot's house, open the door on the ground floor near the river :D
I'll write some simple walkthrough when I have some free time Nayal, thank you for playing the game :D