It is winter, and Jennifer Mace is new to Brooklyn. She visits Prospect Park and meets an old man who feeds the birds, a raven named Napoleon, and a boy named Michael Stewart. Jen and Michael explore a magic island in the lake that turns into an underground tunnel, and a magic tree that temporarily turns them into pigeons. In the spring, Jen gets a bike for her birthday, but a mean boy named Steve tries to steal it. Mike helps her get it back, but almost gets stuck as a pigeon!