Homer is heavily depressed over his life, and Lisa decides to cheer him up by purchasing a raffle ticket at fundraiser at Springfield Elementary School. Homer wins a MyPad and soon becomes obsessed with it until he falls and breaks it. Feeling even more depressed, Homer feels hopeless until Ned Flanders makes a discovery, finding the word "Hope" written on the Simpsons' backyard tree in sap. Everyone, especially Homer, sees it as a miracle. However, reporter Kent Brockman, determined to expose the truth and shatter everyone's hopes, finds a thermal video that shows someone wandering onto the Simpsons' backyard and writing "Hope" onto the tree with maple syrup. Homer is distraught once again until Marge reassures him that since someone wrote the word on the tree, it meant that someone was watching and that the message was for him when he really needed it. Homer agrees and goes back into the house with her. The following night, someone approaches the backyard tree and continues writing "Hope" onto the tree. It is revealed to be a sleepwalking Homer.
The episode ends with a vignette inspired by the French animated short film Logorama.
The name of this episode is a reference to the American book A Tree Grows in Brooklyn by Betty Smith.