Jim and Linda's inability to move objects in the "real" world prevents them from resetting the truck's parking brake or pulling young Janie out of danger.
Their problem is aggravated as they soon learn that at the moment when time "catches up" with them, they must assume the exact positions they had been in five hours earlier, when this whole thing started, or they could remain in that state forever.
They meet an unnamed and seemingly malevolent individual (the "Limbo Being") who earlier experienced the same situation, but failed to make it back in time.
When it reveals that it could take from them their chances to return to reality Jim and Linda come to see just how grave their situation is: one or both could end up being stuck in this state forever.
On discovering that he can move and manipulate items in the crashed plane and car, Jim hits upon a way to save his daughter from death.