What happens on the first night at the House of Shaws?

The protagonist and narrator of the novel, David Balfour, receives a letter from a minister, Mr. Campbell, along with an instruction to travel to the House of Shaws. David is informed that this house was once the home of his deceased father but is now where his uncle, Ebenezer Balfour, resides. David travels a long way to reach the house. As soon as he reaches its vicinity, however, he begins to experience an unexplained feeling of dread. He struggles to find the entrance, as the house seems to be only partially constructed. He hears faint sounds coming from within the house and knocks on the door. The sounds inside abruptly stop, and he expects someone to receive him. However, no response comes.
After contemplating leaving, David decides to knock again. He shouts and pounds the door. An old man answers the door, armed with a loaded gun. David informs him that he is carrying an important letter. The old man asks David to leave, but David is insistent and stays on. David tells the old man his name, and this appears to move the old man. He asks David if his father is dead, to which David makes no verbal response. The old man is able to discern the truth and reluctantly allows David to enter.
David gives the letter to the old man only after learning his identity. He realizes that this man is Ebenezer Balfour, his father's brother. When the man asks David about the purpose of his visit, David conveys to him that he needs some support during this period of crisis but is clear that he does not want any favors. After being asked additional questions about his father's death, David is led to a bedroom so dark that the bed cannot be seen. Because the bed is so unclean, David ends up using his own bed roll to sleep on the floor.