In Chapter 25, Linda writes a letter to Dr. Flint and has it delivered to him as though it has come from Boston. This trick creates a sense of dramatic irony that Linda relishes:
The fact that Dr. Flint had written to the mayor of Boston convinced me that he believed my letter to be genuine, and of course that he had no suspicion of my being any where in the vicinity. It was a great object to keep up this delusion, for it made me and my friends feel less anxious, and it would be very convenient whenever there was a chance to escape. I resolved, therefore, to continue to write letters from the north from time to time.
Linda, Grandmother, and Uncle Phillip all know that Linda is right under Dr. Flint's nose, but he keeps looking for her fruitlessly in Boston. This situation is good for Linda's safety because it keeps Dr. Flint from suspecting that she is still living nearby, where he could reach her. But on top of its strategic usefulness, the dramatic irony represents an even greater triumph for Linda. Dr. Flint has long robbed her of power. He has abused her, threatened her, and led his wife to treat her as a romantic rival who must be defeated. Dr. Flint is the reason Linda must spend years of her life in a cramped space, powerless even to stretch her legs or speak to her children. In this one little way, Linda reasserts her own power over Dr. Flint. Although Grandmother is worried that she is playing with fire, Linda finds it the height of comedy to hear Dr. Flint describing how sure he is that he will catch her in Boston. She can't do much from her garret, but she can make him look a fool by exploiting knowledge that she has and he does not. By writing this dramatic irony into her memoir, she makes a show of outwitting him that readers can enjoy over and over again.
On the other hand, the irony is also sad. Linda's children don't know where she is, either. She listens to Dr. Flint assure Ellen that she will see her mother soon because he believes that he will be able to track her down in Boston. Ellen is too young to fully understand the implications of Linda being caught. This very reason is why Ellen cannot be told that her mother is actually still there in Grandmother's garret. The young child should be able to take comfort in her mother's actual presence, but the need to keep as many people as possible in the dark about Linda's hiding place means that Ellen actually takes comfort in the idea that her mother will be caught by her enslavers.
