It's wrong to sleep with someone else's spouse.
Mark is alone at a bar with his friend Jerry's wife, Maria, and it is time to go home.
Mark wants to get Maria home safely as she is drunk.
Mark drives Maria home and says goodnight and goes home to his own home alone.
Mark asks Maria if she wants to go home with him, and they have sex.
No one is hurt and no friendships are worsened.
Jerry finds out and gets very angry.