One of the worst ways to learn about an affair is to find a love letter.

South Carolina first lady Jenny Sanford says she discovered her husband’s affair in January when she found a letter to the governor from his mistress.

Jenny Sanford told The Associated Press on Friday she told him to end the affair and was shocked this week when she found out he’d gone to Argentina to see his mistress. She says she believed Gov. Mark Sanford had gone somewhere to work on writing a book.