Three short lines, and they say something most people have felt at least once: late at night, loneliness suddenly becomes impossible to ignore. The speaker isn't describing a dramatic event. Nothing happens in the poem. There is only a certain hour, "that time of night," and a quiet realization that arrives with it.
The word "truly" matters here. It suggests the speaker already knew they were alone, in a vague, daytime sort of way, but that knowledge was easy to push aside. Noise, other people, and busyness all help with that. At night those distractions fade, and the fact settles in with full weight.
The mood is hushed, bare, and a little heavy. The plain wording and the lack of punctuation make it feel like a thought drifting through someone's head rather than a speech. The speaker doesn't complain or ask for help. They simply notice, and that restraint is what makes the poem feel honest and familiar.