Time-travel stories have always been problematic, demanding either an extra degree of credulity on the part of the audience or an extra level of explanation on the part of storytellers, which is invariably cumbersome. Frequency handles the troublesome time paradoxes by having John explain how, having altered his past, he now experiences both timelines, as if he's had two pasts that converge in his present. And as changes continue to be wrought in John's past, we see him becoming more and more confused. No doubt the audience can sympathize, at least those of us who try to follow the ramifications of the rapidly accruing time fractures. Luckily, the bond between father and son is so strongly realized in the deeply felt performances of both Caviezel and Quaid that you don't even need to consider the science fiction elements in order to enjoy the film. But if you can suspend your disbelief long enough to allow for the possibility of time shifts, you'll have a far richer experience. --Jim Gay