Henry believes time cannot be changed in The Time Traveler's Wife, but that may not be the case. Time travel is a theoretical science, and any fiction dealing with the idea must develop its own rules.

Precious few franchises actually do so in a consistent manner, largely because temporal mechanics usually serve as a plot device and are therefore secondary to character arcs.

HBO's new TV series The Time Traveler's Wife, based on the best-selling novel by Audrey Niffenegger, is a classic example; as integral as time travel may be to the plot

Traveler's Wife does have a time travel model. It's not stated in conceptual terms, but rather in experiential ones, because for Henry time travel is a lived experience.

According to Henry, time is fixed and it is impossible for him to change anything. He learned that at an early age when, as a grieving child

he desperately attempted to save his mother from a fatal car crash by warning her what was about to happen. And yet, for all that's the case, the truth may be more complex than Henry believes.

On the face of it, then, The Time Traveler's Wife exists in a world where history is fixed and a time traveler can do nothing to change his own personal past.

The truth may, however, be very different. HBO's The Time Traveler's Wife adaptation is written by Steven Moffat, of Doctor Who fame, and it wouldn't be a surprise to see him introduce some twists.