The film will trace Wolverine's past as he discovers the world of mutants and, ultimately, the ominous Weapon X program, which turns people into living weapons.

Wolverine's nemesis Sabretooth "is going to play a big part in it. And there will be a good bit of cameos" of new and familiar mutants, he says. "But you can't give too much away, because fans are pretty hard-core. Their expectations go up a level every time you come out with a new film."