The speaker is a duke who addresses an unknown listener. He draws their attention to a portrait of his former wife, the Duchess, hanging on the wall. The duke reveals that he closely monitored the duchess's behavior and interactions, growing jealous of any admiration or praise she received. He implies he was responsible for her death, which brought a smile he disliked to an end. The duke's possessive and controlling nature is exposed through his boastful yet disturbing monologue. At the end, he invites the listener downstairs while mentioning another artwork, revealing that his companion has been a guest the entire time.