The speaker tells his beloved to look at the flea before them and to note “how little” is that thing that she denies him. For the flea, he says, has sucked first his blood, then her blood, so that now, inside the flea, they are mingled; and that mingling cannot be called “sin, or shame, or loss of maidenhead.” The flea has joined them together in a way that, “alas, is more than we would do.”
As his beloved moves to kill the flea, the speaker stays her hand, asking her to spare the three lives in the flea: his life, her life, and the flea’s own life. In the flea, he says, where their blood is mingled, they are almost married—no, more than married—and the flea is their marriage bed and marriage temple mixed into one.
Though their parents grudge their romance and though she will not make love to him, they are nevertheless united and cloistered in the living walls of the flea. She is apt to kill him, he says, but he asks that she not kill herself by killing the flea that contains her blood; he says that to kill the flea would be sacrilege,“three sins in killing three.”
“Cruel and sudden,” the speaker calls his lover, who has now killed the flea, “purpling” her fingernail with the “blood of innocence.” The speaker asks his lover what the flea’s sin was, other than having sucked from each of them a drop of blood. He says that his lover replies that neither of them is less noble for having killed the flea. It is true, he says, and it is this very fact that proves that her fears are false: If she were to sleep with him (“yield to me”), she would lose no more honor than she lost when she killed the flea.