Indiana Jones and the Last Crusade (Vintage Paperback) by Ryder Windham

The world's greatest adventurer is back!

This time, Indy's on a rescue his father has gone missing on a quest for the Holy Grail, and Indy must put the clues together to locate him. His exploits put him on his father's trail, but treachery isn't far behind. Soon, Indy finds himself walking right into a trap, and he'll have to team up with his father to make it out alive.