Jennet Conant is a genius at finding significant World War II-era stories that have largely gone untold or unnoticed in the more comprehensive chronicles of that period. As the granddaughter of James Bryant Conant, the eminent chemist, statesman and longtime president of Harvard University, she has had particular access to the behind-the-scenes workings of history. From that access have come the dramatic and well-documented narratives Tuxedo Park, 109 East Palace and The Irregulars.

Now Conant is back with A Covert Affair, an equally readable account of larger-than-life Julia Child and her husband, Paul Child—not as culinary pioneers, but in their earlier incarnations as information-gatherers and propagandists for the World War II intelligence network, the Office of Strategic Services. Fascinating as these two figures are, though, the book’s real focal point is their good friend, the daring and alluring socialite and spy Jane Foster.

Julia and Jane were both from wealthy, conservative families in California; Paul, who was 10 years older than Julia, grew up relatively poor in Boston. Idealists all, they volunteered for the war effort and initially served together in Ceylon (now Sri Lanka), working in league with the British. Later, in various configurations, they would continue their government services in Indonesia, China and Vietnam. An impulsive do-gooder, Foster grew incensed that the Dutch, French and English were intent on reasserting their colonial claims in the East once the Japanese were driven out. After the war ended, she argued eloquently and publicly on behalf of the Indonesian resistance movement—one of many political indiscretions that would come back to haunt her when the American government embarked on its witch hunt for Communists.

Conant devotes the last half of her book to showing how the Childs were caught up in Senator McCarthy’s red-baiting. Both were indignant at what they perceived as Foster’s persecution, and both spoke out in her defense, even when evidence filtered in that she might be more culpable in spying for Russia than she admitted. As Foster’s star was sinking, the irrepressible Julia’s was rising. After the war, she took cooking classes to impress hard-to-snare Paul—they were finally married in 1946—then expanded her studies when they were posted to France. By the time Julia’s Mastering the Art of French Cooking was published in 1961 to near-universal acclaim, Foster was living in exile in Paris, embittered, separated from her old friends and contemplating the enormous costs of her political sympathies. Conant’s account of the three friends’ stories is another masterpiece of historical reporting.