being unfaithful to a partner is morally wrong.
Matt and Natalie are dating and Natalie is going to be away on a work trip for a week.
Matt wants to avoid feeling lonely.
Matt calls a friend and invites him over to play video games.
Matt calls his ex-girlfriend and invites her over to his house for an intimate evening.
Natalie is glad Matt had fun with his friend.
Natalie finds out and breaks up with Matt.