Zack Keehbauch- BIG QUESTION

Should someone have to go through so much to believe another? Jacob Portman's grandfather died, and before he passed, Grandpa Portman says things to Jacob about not being safe and goto the island ect. The things said get stuck in his head and starts going a little loopy. He then realizes that he wants to figure out what grandpa Portman was saying about the island. Jacobs dad tells him grandpa was crazy and blah blah blah. Jacob decides to go all the way across the world to see if his grandfather in fact a crazy old geezer. Jacob then goes through hell and back basically just to see if his grandpa was just lying about everything.