Keats’s poem is the story, taken from Boccaccio, about Isabella and Lorenzo, two lovers. Isabella is very beautiful and the sister of two wealthy brothers who are merchants. Lorenzo, on the other hand, is of lower social standing and works for the brothers. It takes a few stanzas for the two to declare their love; once they start meeting surreptitiously the brothers find out and decide to kill Lorenzo. They had decided that Isabella should marry a rich nobleman. The brothers lure Lorenzo to a remote forest, kill him, and bury him on the spot, telling Isabella that he was sent away on business. Isabella is heartbroken, but one night Lorenzo appears in a dream and reveals his fate. Isabella and a nurse sneak off to the forest, find Lorenzo’s grave, and carry his body back to Isabella’s villa, where she combs the corpse’s hair and dresses it. She then buries it in a pot of basil. After that, she is almost always with the basil. She waters it with her tears. The basil grows strong and luxuriant, thriving far more than any of her other plants. The brothers notice this, and, in suspicion, steal the plant and find Lorenzo’s corpse. Afraid of being found out, they flee. Isabella dies mourning for her lost pot of basil.
Some themes you might want to consider include the following:
Emotions over logic—You might want to think about the all-consuming nature of Isabella and Lorenzo’s love, how Isabella learns in a dream about Lorenzo’s fate, or about the rationale behind retrieving his corpse and planting it in a flower pot. None of these things are “logical,” but they serve as the "logic" of the story nevertheless.
Death as escape—While neither Lorenzo nor Isabella wish to die, their deaths serve as a kind of reunion. Lorenzo’s appearance in Isabella’s dream also suggests that the truth of their love somehow can transcend death.
Unity with nature—Lorenzo literally returns to nature, first in his forest grave, then in the pot of basil. The image of Isabella nourishing the plant with her tears suggests that the basil is a kind of living intercession between herself and her dead lover. The plant’s vigor is symbolic of the the strength of their bond.
Nature vs industry—The brothers, for whom ”many a weary hand did swelt / In torched mines and noisy factories,” represent evil in the poem; they function not only to deny Isabella what she desires, but also subvert and pervert the natural order by murdering Lorenzo. If Lorenzo and Isabella represent nature and emotion, the brothers represent industry and logic.
Class consciousness—While Lorenzo and Isabella seem unconcerned about their differing socioeconomic status, the brothers are keenly aware of it. As capitalists, the brothers can be understood to represent a kind of economic perversion, one which enslaves men like Lorenzo and subverts emotional norms.