The train goes into a dark tunnel and a few seconds later there is the sound of a loud slap.
When the train emerges from the tunnel, the Frenchman has a bright red hand print on his cheek. No one speaks.
The old lady thinks: The Frenchman must have groped the blonde in the dark, and she slapped his cheek.
The blonde thinks: That Frenchman must have tried to grope me in the dark, but missed and fondled the old lady and she slapped his cheek.
The Frenchman thinks: The American must have groped the blonde in the dark. She tried to slap him but missed and got me instead.
The American thinks: I can't wait for another tunnel, so I can smack that Frenchman again.