durring a ride on a train

A train speeds away in a beautiful landscape. In one of the compartments are
4 people, sitting opposite to each other: a high-ranking general, a private and a middle-aged woman and her pretty, sexy daughter.
The ride is rather uneventful until the train enters a tunnel...complete darkness...and suddenly there is a loud slap!...When the train leaves the tunnel all passengers have indescribable looks on their faces, no one says a word...but here is what they think:

-the mother: I've brought up my daughter well - she knows how to handle insolent men

-the daughter: hmm.. my mom still seems to have a strong sex-appeal on men

-the general: damn, the private gets all the fun and I'm getting the beating

-the private: heh, in the next tunnel I'll slap him again