You're on your honeymoon at an exclusive couples-only resort. You receive a note, warning you to 'Beware of the couple at the table nearest to yours'. At dinner that night, five other couples are sitting close by, but none of their tables is any nearer or further away than any of the others. It's almost as if someone has set the scene in order to make the warning note meaningless. Why would anyone do that? You have no idea.