In the first book, Rinaldi introduces Henry to Catherine Barkley; Henry attempts to seduce her, and their relationship begins. While on the Italian front, Henry is wounded in the knee by a mortar shell and sent to a hospital in Milan. The second book shows the growth of Henry and Catherine's relationship as they spend time together in Milan over the summer. Henry falls in love with Catherine and, by the time he is healed, Catherine is three months pregnant. In the third book, Henry returns to his unit, but not long afterwards the Austro-Germans break through the Italian lines in the Battle of Caporetto, and the Italians retreat. Henry kills an engineering sergeant for insubordination. After falling behind and catching up again, Henry is taken to a place by the "battle police", where officers are being interrogated and executed for the "treachery" that supposedly led to the Italian defeat. However, after seeing and hearing that everyone interrogated is killed, Henry escapes by jumping into a river. In the fourth book, Catherine and Henry reunite and flee to Switzerland in a rowboat. In the final book, Henry and Catherine live a quiet life in the mountains until she goes into labor. After a long and painful birth, their son is stillborn. Catherine begins to hemorrhage and soon dies, leaving Henry to return to their hotel in the rain.