And every night, about midnight, I turned the latch of his door and opened it – oh so gently! (3)
If the old man leaves his door unlocked, it means he trusts the narrator, or (if he's bedridden) he might not have a choice. Either way, this is why we don't go to sleep until well after midnight.
And every morning, when the day broke, I went boldly into the chamber. (3)
We wonder if he stays up all night waiting by the door, or if he takes a break. It's not really clear. What a wretched, isolated picture of home.
And now a new anxiety seized me – the sound would be heard by a neighbour! (7)
Home can be an uncomfortable place when we fear our neighbors, or when we have suspicious characters like the narrator living near by. This common anxiety is brought to extremes in this story, echoing what we sometimes see if real life.