Jacob's been in and out of the foster care system most of his life--until he stumbles into Mr. Fielding, who takes him in. They get along well together until a car accident kills Mr. Fielding.
But Jacob has a secret. Right before the crash, Mr. Fielding whispered "You are indestructible" to Jacob, which saved his life. Jacob's not sure, but he thinks he can't die. And when he accidentally writes the same phrase on Olivia's cast, he puts both their souls in danger.
The story seems a little odd, and it is. There is a lot of suspension of disbelief here, but the story itself is interesting and engrossing. Most of the book is spent trying to see the limits to this "power" of Jacob's, with Olivia getting more and more obsessed with it. When Jacob and his best friend realize they shouldn't have been playing with the idea, it's almost too late to save Olivia. Lots of action and suspense. You just have to ignore some of the most implausible ideas.