The cave dwellers who give their name to the title of Maine author Richard Grant's new novel are two types of people. They are the influential politicos and policymakers who reside in the affluent Washington, D.C., neighborhood of Kalorama — "or simply the Caves," and they are the "shadowy denizens" who attend the salons of a baroness in prewar Berlin — "the sort of people for whom there was no place in the New Germany," scoffs one Nazi. "Political primitives. Cave dwellers. No one to worry about." Individuals from each camp conspire and collide in an intelligent, sharply focused, high-stakes drama.

Grant opens in Berlin in 1937 and introduces characters unswayed by the current nationalistic fervor. His baroness is horrified at the incessant marching, banners and beer-hall songs in the city, and angry about how "that wretched Austrian cur" is dirtying the country's reputation. At one of her parties, a high-ranking intelligence officer takes young Lt. Oskar Langweil aside, and after testing his allegiance by bewailing the state of the nation, recruits him to help save the Fatherland.

Oskar is given a false identity and sent from "great, ugly, beloved" Berlin to "drowsy little backwater" Washington. However, six weeks in and his cover is blown, his mission jeopardized. He is put in contact with Lena, an exiled German Socialist, who helps him with an even more daring mission: "The whole tangled and frightful business of resistance and spying and reinfiltrating the Reich under the eyes of the SS."

"Cave Dwellers" has much in common with Grant's 2006 debut novel, "Another Green World." Both books draw on the run-up to war, toggle between the U.S. and Germany, and deftly blend fiction, historical fact and literary allusion. Unfortunately, the main flaw in Grant's first book is also a marring presence in his latest. Simply stated, Grant feeds us too many characters. People come and go, and not all are fleshed out. When some reappear, having been only fleetingly glimpsed earlier, we struggle to remember who's who — and, crucially, who means what to whom. In places, we share the baroness' confusion on the first page: "Who knew what anybody was anymore?"

The novel is at its most effective — indeed, its most thrilling — when Grant cuts back and homes in, building action and stoking suspense around the escapades of Oskar, Lena and the two other unlikely fugitives they pick up on the way: a U.S. senator's son and a gay SS officer. With the treacherous and conniving Col. Kohlwasser on their tail, the motley group soon becomes the most wanted people in the Third Reich.

What begins as an operation to avert war turns into a transatlantic, cross-country cat-and-mouse chase and quest for survival. As Grant's outlaws run, they stick together, and his novel hastens toward a conclusion that manages to excite but at the same time examine, most notably, questions of trust, loyalty and patriotism.

Malcolm Forbes has written for the Times Literary Supplement, the Economist and the Daily Beast. He lives in Edinburgh, Scotland.

Cave Dwellers
By: Richard Grant.
Publisher: Alfred A. Knopf, 339 pages, $27.95.