The speaker dreams of walking down a street that is completely empty, yet full of sound: people are crying, though no one can be seen. The repetition of "empty street" at the end of nearly every line makes the place feel like a trap, as if the speaker keeps circling the same bare spot. Even calling out brings nothing back, which deepens the sense of isolation and helplessness.
The last stanza shifts things. The speaker finds an old picture of the same street, now crowded with smiling people. That contrast hints at loss: something happened to turn a lively place into a silent one, though the poem never says what. The poem doesn't explain this, so the reason is left for the reader to guess. The mood is haunting and sad, tinged with nostalgia. The speaker seems to long for what the street once held, and the crying heard in the emptiness suggests that the loss still hurts.