1. A man sits in his cold cottage on a stormy night. Porphyria, his lover, arrives and makes the cottage warm and comfortable, before sitting down next to him
2. He ignores her while she's flirting with him - he seems upset with her. However, he decides that she loves him and that she belongs to him - he wants to preserve the moment, so he strangles her with her own hair. It's clear that the speaker is mentally disturbed.
3. He opens her eyes and spends the rest of the night sitting with her dead body.