In 1952, adolescent lovers, Haskell and Jennifer, are separated following an accident in which Jennifer's parents are killed. A second accident twenty years later reunites them and renders them able to travel through time. Unencumbered by corporeal form, they may choose to go forward to the future or back to witness historical events. They may also travel sideways through the second and third dimensions of time, visiting alternate (what might have been) realities. Consistent with the many worlds interpretation of quantum physics, time—like space—is three-dimensional, with a nearly infinite number of constantly dividing and diverging time streams, each stream containing its own unique reality.