By Anne Perry

Ballantine. 338 pp. $25.95

Anne Perry, the prolific British mystery writer, is the author of two series set in Victorian England, and last year she published "No Graves as Yet," the first novel in a new series set before and during World War I. "Shoulder the Sky" takes place in the spring of 1915 and continues her story of murder and espionage.

The story centers on the three Reavley siblings. Joseph, the oldest at 35, is an army chaplain who tries to comfort soldiers amid the trench warfare of Flanders but finds his own faith sorely tested. His sister, Judith, is close by as a volunteer ambulance driver who has become the driver for the British commanding general. Matthew is an intelligence officer in London, where he is secretly trying to solve the mystery that has hung over the Reavley family since the opening pages of the previous novel.

That novel began with the siblings' parents being killed in what first seemed to be an auto accident but proved to be murder. The night before his death, their father, a former member of Parliament, called Matthew and reported that he had evidence of a conspiracy that could change the future of the world. With Europe at the brink of war, this proves to be a proposed treaty "between Kaiser Wilhelm II and King George V agreeing that England should abandon France and Belgium to the German conquering army, in return for which England and Germany together would form an empire to divide the world between them." As part of the inducement, the Germans would help the Brits regain their former colonies (that would be us). No one knows if King George would approve such a plan (he is, as it happens, the kaiser's cousin) but the Reavleys assume that such a deal -- even if it would save hundreds of thousands of lives -- would be dishonorable and must be stopped at all costs. They don't know who is behind the plan, but they assume he is highly placed. They bitterly refer to him as the Peacemaker.

Perry places each of the siblings in the midst of dramatic events. Joseph lives in the trenches with the soldiers, with bombs and rats, tending to the wounded and wrestling with his faith amid senseless slaughter. When an arrogant newspaper reporter is murdered, everyone else says "good riddance," but Joseph's conscience makes him turn detective to find the killer. In time he learns that the dead man may have been an agent of the Peacemaker, who encourages reporters to write about the horrors of the war to undermine British morale. Meanwhile, 24-year-old Judith has romantic feelings for the general for whom she works, despite his age of 48 and wife back home. In time she confides in him about the Peacemaker, an indiscretion that leads to tragedy. In London, Matthew suspects several people of being the villain, including his own boss in the Secret Intelligence Service, and he is fearful of trusting anyone.

Perry weaves into her narrative brief mentions of real events, including the death of the poet Rupert Brooke, the zeppelin bombing raids on English coastal cities, the sinking of the Lusitania, the battle at Gallipoli, German attempts to encourage a Mexican invasion of the United States and British contempt for President Woodrow Wilson's policy of neutrality: "In his mind he's still a schoolmaster who is going to arbitrate between two unruly children in the playground."

"Shoulder the Sky" (the title is from a poem by A.E. Housman) ends with plots still spinning and a third installment of the saga looming in the distance.

I am of two minds about this novel. Perry's fans will probably find it an entertaining, suspenseful thriller -- and it is, because Perry is a skillful purveyor of popular fiction who uncorks all the tricks of romance, melodrama and comic relief to keep her readers engaged. But anyone who chooses at this late date to write about the first World War confronts not only some of the most terrible slaughter in human history but some of the most impassioned writing of the past hundred years.

Ernest Hemingway, in "A Farewell to Arms," has Frederick Henry say, "Abstract words such as glory, honor, courage, or hallow were obscene beside the concrete names of villages, the numbers of roads, the names of rivers, the numbers of the regiments and the dates." Rupert Brooke left poems, written in the months before his death ("If I should die, think only this of me" or "Blow out, you bugles, over the rich Dead!"), that are incomparable. F. Scott Fitzgerald, in "Tender Is the Night," has Dick Diver visit a Flanders battlefield and say to Rosemary: "See that little stream -- we could walk to it in two minutes. It took the British a month to walk to it -- a whole empire walking very slowly, dying in front and pushing forward behind." As even these fragments suggest, if Perry's novel is a skillful popular entertainment, it is also a reminder of the limitations of such fiction in dealing with human tragedy on a scale that should make the heavens weep.