A British biplane soaring over the desert finds itself under fire from German gunners, resulting in a crash that leaves the pilot badly burned. He is fortunately rescued by a group of Bedouin.

Among the chaos of World War II, Hana, a combat nurse with the Royal Canadian Army Medical Corps, learns about the death of her boyfriend from a dying soldier. In October 1944 Italy, she finds herself caring for a severely burned patient who is unable to recall his own name. The only clue to his identity comes from a copy of Herodotus’s Histories, which contains personal notes, pictures, and mementos.

Hana endures the trauma of watching a fellow nurse perish and, believing herself to be a jinx to those around her, seeks refuge in a bombed-out monastery with her unknown patient, who requires special care during their hospital’s relocation. Enter Lieutenant Kip, a Sikh sapper from the British Indian Army, who, alongside Sergeant Hardy, is tasked with clearing explosive remnants left by the Germans. He soon joins Hana and her patient.

As fate would have it, David Caravaggio, a Canadian Intelligence Corps operative scarred by torture from the Germans, arrives at the monastery too. As he interrogates the patient, fragments of his past begin to emerge through a series of poignant flashbacks. During this time, Hana and Kip find solace in each other’s company, igniting a tender romance amidst the backdrop of war.

The story intertwines with that of Hungarian cartographer László Almásy, who, in the late 1930s, embarks on an exploration across the Sahara with a diverse expedition team that includes his good friend Peter Madox and the British couple, Geoffrey and Katharine Clifton. Almásy stumbles upon the hidden Cave of Swimmers, rich with ancient cave paintings, setting up a documentary endeavor while simultaneously delving into a forbidden love affair with Katharine.

As their attraction deepens, Almásy pens heartfelt notes about Katharine, which she discovers tucked within his writings. Their clandestine romance flourishes in Cairo, where he surprises her with a silver thimble. However, lurking shadows reveal Geoffrey’s knowledge of their affair, leading to tension. The onset of war abruptly sunders their connection, forcing Katharine to escape from their relationship due to the risks involved.

Amidst this turmoil, Caravaggio seeks vengeance for his suffering caused by the Germans, pinpointing Almásy as a potential traitor. In a confrontational moment, he questions Almásy about the fate of the Cliftons, to which Almásy cryptically admits, > “Maybe… I did.”

As Almásy recounts a haunting memory from 1941 when Geoffrey confronts him in a biplane, a tragic series of events unfolds, leading to an attempted double murder-suicide. He discovers Geoffrey deceased and severely injured Katharine, whom he carries to the safety of the Cave of Swimmers. Here, she confesses her enduring affection for him, encapsulated by the silver thimble she wears.

Desperate to ensure her safety, Almásy leaves her provisions and his journal before embarking on a grueling three-day trek across the desert in search of help. However, upon reaching British-held El Tag, he is detained under suspicion of being a spy. After a thrilling escape, he eventually locates German forces and trades maps for fuel to return to the cave, only to discover Katharine has died. Their tragic reunion culminates in a fateful second plane ride, echoing the initial crash that began this harrowing tale.

Ultimately, as the story draws to a close, Caravaggio releases his desire for retribution after learning of Almásy’s heart-wrenching journey. Kip departs once his mission is complete, yet he promises Hana they will reunite. Amidst her sorrow, Hana fulfills Almásy’s final wish by administering morphine, allowing him a peaceful departure as she reads Katharine’s last letter. The next day, holding Almásy’s treasured book, she journeys with Caravaggio to Florence, carrying the weight of their intertwined destinies.