An alien land his spaceship and shows up carrying what appears to be a reference book or manual.
HOW TO SERVE MAN
Earthlings take it as proof that the alien is here to help us and is no threat and means us no harm. He invites earthlings to come with him to his planet. Some trusting ones go aboard with him and too late it is revealed that
HOW TO SERVE MAN
is a cookbook.
How often have you been deluded by a series of words whose meaning you didn't really understand until it was too late?