Theme in Porphyria's Lover

The theme in Porphyria’s Lover, by Robert Browning, is developed by an alluring name and beginning. There is a terrible storm going on outside, perhaps the reason the speaker seems distraught, like he is contemplating something. “I listened with heart fit to break. When glided in Porphyria; straight” (lines 5 & 6) The speaker was worried his lover would not care enough about him to come out in a storm to see him.
Once she is there he changes his attitude quick. “So, she was come through wind and rain” (line 30). Suddenly the speaker is very sure of himself. He now knows that she loves him. “Happy and proud; at last I knew Porphyria worshipped me; surprise (lines 32 & 33) Now that he is convinced that he has her undivided affection, he doesn’t want it to end. It is too perfect in his eyes to stay this way, so he finds a way to keep her perfect for him. “In one long yellow string I wound Three times her little throat around, And strangled her. No pain felt she” (lines 39 – 41); The speaker has convinced himself that strangling her was the right thing to do and that he caused her no pain.
He also thinks that this is what Porphyria secretly wanted. This way they could always be together. “That all is scorned at once is fled, And I, its love am gained instead” (lines 54 & 55)! The speaker is happy that Porphyria is at his side and convinced that they will now share the perfect love.