Someone has died, and the speaker is remembering that moment. The opening line sets it up simply: it was silent as they passed, while the speaker and others were busy joking and laughing. That contrast, a happy noise on one side and a quiet death on the other, gives the poem its sting.
From there the speaker turns thoughtful and a little wistful. They wonder what the person's mind last held on to before it slipped loose from "this dream," a phrase that suggests life itself feels dreamlike. The speaker admits we may never know, but finds comfort in the idea that a silent death is a lucky one, without clinging or thrashing.
The ending is tender rather than grim. The speaker imagines the person reliving old memories and laughs, then says goodbye with "Bon voyage!" and an open invitation to return. The mood is calm, gentle, and quietly hopeful, with grief softened by affection and a wish for peace.