The speaker is being pushed for answers. Someone keeps pounding at them, demanding to know why they won't respond. The poem's reply is quiet and a little startling: the silence isn't coldness or stubbornness. It's thinking.
What the speaker is thinking about is the last lines. They are weighing whether they should have "accepted the flames" for this person "once again." The flames suggest suffering or punishment, something painful the speaker took on so the other person wouldn't have to. The word "again" matters, because it hints this has happened before, and that the speaker is now doubting whether the sacrifice was worth it.
The mood is tense but controlled. The other person is loud and insistent, while the speaker is still, almost weary. The dash at the end, with no conclusion, leaves the question hanging. We don't learn the answer, and that unresolved feeling of hurt, doubt, and held-back anger is what stays with the reader.