After years of being humiliated and oppressed by her husband Frank, Susan decides to slowly poison him until he dies. Living with them is Susan's bachelor brother.

At first, the brother agrees to Susan's scheme. Frank was mean, and his failures at work had made him meaner. A conservative utilitarian, he disliked Susan's liberal generosity towards the impoverished.

After months of consistent poisoning, however, Frank becomes a more feeble creature worthy of sympathy. The brother begs Susan to reconsider, but Susan claims she'll never be free until Frank dies.

After his death, Susan expresses remorse and her brother helps corroborate her lies about Frank's death.