Allen Faulkner, a former British Army colonel turned mercenary, arrives in London to meet merchant banker Sir Edward Matheson. The latter proposes an operation to rescue Julius Limbani, the imprisoned President of a southern African nation who is due for execution by General Ndofa. President Limbani is held in a remote prison in Zembala, guarded by a regiment of General Ndofa's troops known as the "Simbas".