Jonathan's Journal

A century-old soldier's diary wasn't meant for him, but he found himself in the story.

An art historian living a quiet life in Southern California never expects his late mother's antique collection to contain a mystery that will upend him. Yet hidden among her rare books is a meticulously handwritten World War I diary, signed only with the initials "J.F.W." The coincidence is unsettling. The contents are even more so.

The diary's author-a British cavalryman turned infantry officer-records his...