Simplify the following text for a Grade 9 native English-speaking person.
Original: Thinking that Susanna is meeting the Count behind his back , Figaro complains to his mother , and swears to be avenged on the Count and Susanna , and on all unfaithful wives .
Simplified: Thinking that Susanna is secretly meeting the Count , Figaro complains to his mother , and swears to take revenge on the Count and Susanna .