WARBURG IN ROME. By James Carroll. Houghton Mifflin Harcourt. 364 pages. $28.

James Carroll's newest novel takes place in the waning years of World War II, when Europe is awash with intrigue and the victors deal with the aftermath.

Rome is the setting for David Warburg, newly arrived director of the U.S. War Refugee Board, whose main purpose is seeking out the thousands of "displaced persons," mainly Jews, taking refuge in Rome. He meets Marguerite, an Italian Red Cross worker, an American priest, an American military officer and many others with secrets and inside information.

As he searches for refugees in hiding, the shocking story of the Vatican's role in the "ratline," an escape route for Nazi war criminals, emerges. Even more shocking is that the Allies often have been complicit. Swirling among the many characters, fictional and nonfictional, are the unresolved horrors of war, on both sides.

The moral issues are huge, and the intricate details provided by Carroll as he grapples with large and complex issues hinder the suspense and continuity on which a thriller depends. The diligent research of a hugely difficult subject is obvious and perhaps better suited for a scholarly tome.

Reviewer Frances Monaco is a writer in Charleston.