In 1935, T. E. Lawrence dies in a motorcycle accident. At his memorial service at St Paul's Cathedral, a reporter tries, with little success, to gain insights into the remarkable, enigmatic man from those who knew him.

The story then moves back to the First World War. Lawrence is a misfit British Army lieutenant who is notable for his insolence and education. Over the objections of General Murray, Mr. Dryden of the Arab Bureau sends him to assess the prospects of Prince Faisal in his revolt against the Turks. On the journey, his Bedouin guide, Tafas, is killed by Sherif Ali for drinking from his well without permission. Lawrence later meets Colonel Brighton, who orders him to keep quiet, make his assessment, and leave. Lawrence ignores Brighton's orders when he meets Faisal; his outspokenness piques the prince's interest.

Brighton advises Faisal to retreat after a major defeat, but Lawrence proposes a daring surprise attack on Aqaba. Its capture would provide a port from which the British could offload much-needed supplies. The town is strongly fortified against a naval assault but only lightly defended on the landward side. He convinces Faisal to provide fifty men, led by a pessimistic Sherif Ali. The teenage orphans Daud and Farraj attach themselves to Lawrence as servants. They cross the Nefud Desert, considered impassable even by the Bedouins, and travel day and night on the last stage to reach water. One of Ali's men, Gasim, succumbs to fatigue and falls off his camel unnoticed during the night. When Lawrence discovers him missing, he turns back and rescues Gasim, and Sherif Ali is won over.

Lawrence persuades Auda Abu Tayi, the leader of the powerful local Howeitat tribe, to turn against the Turks. Lawrence's scheme is almost derailed when one of Ali's men kills one of Auda's because of a blood feud. Since retaliation by the Howeitat would shatter the fragile alliance, Lawrence declares that he will execute the murderer himself. Lawrence is then stunned to discover that the culprit is Gasim, the man he risked his own life to save, but Lawrence shoots him anyway.

The next morning, the Arabs overrun the Turkish garrison. Lawrence heads to Cairo to inform Dryden and the new commander, General Allenby, of his victory. While crossing the Sinai Desert, Daud dies when he stumbles into quicksand. Although his report of Aqaba's capture is initially disbelieved, Lawrence is promoted to major and given arms and money for the Arabs. He is deeply disturbed and confesses that he enjoyed executing Gasim, but Allenby brushes aside his qualms. Lawrence asks Allenby whether there is any basis for the Arabs' suspicions that the British have designs on Arabia. When pressed, Allenby states that there is none.