This is one of many excellent narrative poems that Robert Browning produced featuring an unreliable narrator who, perhaps much like the unreliable narrators of Poe's work, is clearly on the edge of lunacy if not completely mad. One of the key themes of this poem is possession. The narrator desires to possess his love completely, and it is this that drives him to commit the act that eternalises his love, for he realises that Porphyria does not have the strength to entrust herself into his care completely:
Murmuring how she loved me—she
Too weak, for all her heart's endeavour,
To set its struggling passion free
From pride, and vainer ties dissever,
And give herself to me for ever.
Yet this is not enough for the speaker of the poem. Reflecting that there and then, whilst they are embracing, she was "his" perfectly and truly, he wraps the tresses of her hair around her neck three times and strangles her to preserve this perfect moment. Somewhat ironically, towards the end of the poem, the narrator reflects:
Porphyria's love: she guess'd not how
Her darling one wish would be heard.
And the poem ends with their continued togetherness that remains uncommented upon by God, perhaps reflecting the narrator's belief that he has done the right thing.