X: X Marks the Spot

In the third and perhaps the best Indiana Jones movie, Jones and his friends are searching for clues in a historic library and they find a large roman numeral ten, X, on the floor.  Jones observes, 'X marks the spot' in his wry way.  It was funny in the movie and was quite clever but when writing a book, X usually shouldn't mark the spot.

Hopefully as I write my fantasy novels, I include many twists and surprises.  The answers sought by my characters need to be difficult to find.  Victory must be earned and not by something so easy as finding the X marking the spot.  Wrong turns must be taken along the incorrect fork in the road. 

I'm sure you've read books or watched movies where the hero stumbles on something way too conveniently.  I remember a scene from one of the CSI shows where one of the investigators is buying a cup of coffee from a street vendor and a crow flying over drops an eyeball in her cup.  Of course, this leads to the discovery of a body and the show goes on.  What are the chances such a coincident would occur?

Can you give an example where a mystery was solved without the hero working for the answers? Or have you read a book or seen a movie recently where the story ending was so obvious it seemed marked with a big X?