Frederic and Catherine fall in love as Frederic slowly heals.
After his knee heals, he is diagnosed with jaundice but is soon kicked out of the hospital and sent back to the front after being discovered with alcohol.
The inspiration for Catherine Barkley was Agnes von Kurowsky, a nurse who cared for Hemingway in a hospital in Milan after he had been wounded.
He had planned to marry her but she spurned his love when he returned to America.
In the final book, Frederic and Catherine live a quiet life in the mountains until she goes into labor.
The novel was based on Hemingway's own experiences serving in the Italian campaigns during the First World War.
He heads to Milan to find Catherine only to discover that she has been sent to Stresa.
In the fourth book, Catherine and Frederic reunite and spend some time in Stresa before Frederic learns he will soon be arrested.
By the time he is sent back, Catherine is three months pregnant.
In the third book, Frederic returns to his unit, and soon discovers morale has severely dropped.