W.E. Johns 
Worrals Goes Afoot [EPUB ebook] 

Worrals and her friend Frecks were settling down to a peaceful, uneventful life when the Secret Service once again called on them to serve their country. An important highway was being built across the sands of the Middle East, and rumours of a planned insurrection among the native workmen had come to the ears of those in authority.

It was discovered that arms and ammunition were being supplied to these men from an unknown source. What was the motive? Who was financing the gun-running? Who was distributing the weapons? Try as they might, the Secret Service had been unable to solve the mystery. So Worrals and Frecks set out on an adventure which took them into Egypt and the heart of the Sinai Desert.