This historical account focuses on the rise and career of Mohammed bin Abdulla Hassan, known to the British as the "Mad Mullah," from 1899 until his death in 1921. The narrative describes the Mullah as a "Lord Temporal as well as a Lord Spiritual," tracing his evolution from a religious reformer to a militant leader. The author acknowledges that no Englishman ever saw the Mullah during his twenty-one-year revolt, making the work a reconstruction based on intelligence reports and official records.

Beyond a biography, the work serves as a detailed record of Great Britain’s connection with its Somaliland Dependency during a period of intense military struggle. It includes accounts of various expeditions, notably the 1919 campaign involving the Air Force, which led to the downfall of Dervish power. The book addresses the "refractory nature" of the Somali landscape and its people, providing an authoritative account of British policy.

The text is supplemented by numerous illustrations, maps, and facsimile letters, including a personal portrait of the Mullah based on Intelligence reports. It provides insights into the complex Dervish social structures, their fortified strongholds like Tale, and the final military operations that re-established British prestige in the region.