A woman walks toward a light at the end of a tunnel, and the poem never lets her arrive. The repeated "She walked and walked..." gives the feeling of a long, tired journey, and the trailing dots make it seem like it could go on forever.
The light is tied to "the thing she loved the most / And the thing she could never have." That pairing is the heart of it: she is drawn toward what she wants most, even though it is out of reach. The speaker watches from a distance and sounds quiet and sorrowful rather than angry.
The phrases "Bright as the moon" and "Dark as the night sky" open and close the poem, so the whole thing feels like a loop. Light and darkness sit side by side. Because the image of a tunnel's light can also suggest death, the poem may hint at something final, though that is an inference. Either way, the mood is haunting, longing, and heavy with resignation.