“My Last Duchess” has a profoundly sinister tone. The term sinister describes an impression that something harmful or evil either is happening or is about to happen. The sinister tone that arises in Browning’s poem relates both to the past and the future. This feeling is already present in the poem’s opening line, where the speaker refers to his deceased wife as “my last Duchess.” He means that she was the previous Duchess, but his use of the word “last” also implies a disturbing sense of disposability. The sinister feeling arises again when the Duke quotes Fra Pandolf’s words about his experience of painting the Duchess’s portrait (lines 17–19):

                                  “Paint
     Must never hope to reproduce the faint
     Half-flush that dies along her throat.”

As we soon learn, this blushing “half-flush” relates to what the Duke considered his late wife’s excessively flirtatious demeanor, which in turn led him to orchestrate her death. The fleeting reference to a “Half-flush that dies along her throat” may be read as a sinister implication that the Duke had her strangled. All these details produce a foreboding sense when we learn that the Duke is on his way to negotiate marriage to another young woman. Hence we begin to wonder: What kind of violence might befall her?