Read it through once

“It was only yesterday that the chance came. I may tell you that, besides Mr. Rucastle, both Toller and his wife find something to do in these deserted rooms, and I once saw him carrying a large black linen bag with him through the door. Recently he has been drinking hard, and yesterday evening he was very drunk; and when I came upstairs there was the key in the door. I have no doubt at all that he had left it there. Mr. and Mrs. Rucastle were both downstairs, and the child was with them, so that I had an admirable opportunity. I turned the key gently in the lock, opened the door, and slipped through.