by P.C. Wren · 1924
When their aunt's priceless sapphire, the 'Blue Water,' vanishes, three brothers each vanish in turn to shield the others from suspicion, enlisting under false names in the French Foreign Legion. Years later a fellow officer arrives at a desert garrison to find every man of its besieged fort dead at his post and the fort's commander stabbed with no killer in sight, and pulls at the thread that unravels the brothers' sacrifice.