Archer's luck / Ed Roberts.

When drifter Lew Archer meets a priest, while travelling along a lonely road in Texas; he thinks nothing of it. But this chance encounter sets in motion a train of events which, strange to relate, sees Archer undertaking to escort a party of nuns through hostile territory to start a school on the Mexican border. With war and bloodshed around them, it will be a miracle if they manage to make their way to safety. If anybody can help them achieve their aim it is Lew Archer, although we he should take the trouble to do so is a mystery to everybody; including Archer himself!