A speaker stands before something huge and frightening, a door that stretches from sky to floor and stares back with "big, black eyes." The door seems to stand for a fear or pain they have kept buried, and the poem is really about whether to face it. The refrain makes this clear: the key is not somewhere far off but "confined in my soul," hidden beneath tears. The thing they dread opening is also part of them.
Each stanza offers a different choice. The speaker could open the door, run and hide in a "trivial hollow," or break the door down and risk drowning in what lies behind it. The questions are never answered, which leaves the speaker stuck at the threshold.
The mood is tense and heavy, with a quiet sadness. The repeated refrain works like a loop of anxious thoughts that keeps returning to the same spot. Still, the last choice, to "see what my fears see," hints at a flicker of courage.