Why does Frank want to memorize "The Highwayman" and read it back to Patricia?

Patricia Madigan, who is dying of diphtheria at fourteen. Patricia gives Frank a book that introduces him to Shakespeare, which affects him deeply. She also recites verses from the popular poem, "The Highwayman." The nurse doesn't like the two ill children speaking, however, and moves Frank to a ward by himself. There he learns that Patricia has died. Frank has Seamus ask his pub friends what happens at the end of "The Highwayman," and Seamus memorizes the last verses for Frank. He wants to read it to Patricia to ease her suffering as she dies.