The famous short story "The Lady With the Pet Dog" by Anton Chekhov tells of a meeting between Dmitri Gurov, a married banker approaching middle age, and a young married woman named Anna Sergeyevna. Each is vacationing alone in Yalta, and they begin spending time together. When their holiday is over, Gurov cannot stop thinking about Anna. He goes to see her in her home city, and she agrees to come to Moscow to meet him. They realize that they are in love and begin an affair.
Both Gurov and Anna go through profound changes in this story, and these changes have to do with falling unexpectedly in love. Gurov has a wife and three children, but he is unhappy in his marriage. He has been a lady's man, picking up women and having affairs, but they have all been unimportant and only for sensual gratification. They have left him feeling unhappy and unfulfilled. All this changes when he meets Anna. For the first time in his life, he falls in love. The depth of his emotion takes him by surprise, and the true love that Anna bestows upon him humbles him and makes him consider his age and how unhappy he really is in the present circumstances of his life.
As for Anna, she undergoes significant change as well. When she meets Gurov, she is aware that she is unhappy, but she considers herself honest and pure and doesn't want to do anything sinful. However, after she falls in love with Gurov, she is willing to meet him and start an affair, something she would never have considered previously. In this way, she undergoes a significant character transformation due to the depth of her feelings for Gurov.