At the dinner party that opens Sarah Blake’s second novel, “The Postmistress,” a World War II reporter asks, “What would you think of a postmistress who chose not to deliver the mail?” One woman cries in delight, “I’m hooked already,” adding a moment later that such behavior is “monstrous. ... If it’s real, then it’s horrible.”

The novel is set in 1940 and 1941, as Londoners struggle to survive the Blitz and Americans debate whether to join the struggle against Nazi Germany.

Blake follows three women. Frankie Bard is a “leggy blonde” from Greenwich Village who goes to London as a radio correspondent because she believes that’s where the action is. She is “a Diana who wore her red lips like a sword. And the page on her lap ... a shield.” Meanwhile, back on Cape Cod are two women who listen to her broadcasts. Emma Fitch is the young, lonely, pregnant wife of the town doctor, Will; Will has gone to London after a mother dies in childbirth on his watch. And there is the postmistress for the Cape Cod village of Franklin, Iris James, who loves order above all else and believes “if there was a place on earth in which God walked, it was the workroom of any post office in the United States of America.”

When we meet Iris, she is visiting a Boston physician so he can examine her and confirm for Harry Vale, the man who has caught her eye, that she is indeed a 40-year-old virgin. Harry is not the sort who would care. He cares mostly about keeping an eye out for German U-Boats off the dunes of Cape Cod – which he does when he isn’t courting Iris or listening to Frankie Bard on the radio.

Now, the idea that there may have been U-Boats off the U.S. coast is not preposterous; occasionally there were. What feels a tad heavy-handed is Harry’s belief that “if the Germans were to attack, they’d land on the back shore, taking Franklin first, and then sweep up the Cape into Boston.” He wants the flagpole at the post office lowered so the invaders can’t use it as a marker.

I am sure that in the summer of 1941 there were many people who did believe either that England might succumb to the bombing (though their numbers had diminished since the Blitz had begun and Britain had shown its resolve) or that the Germans would invade the U.S. But Henry’s fixation turns an otherwise immensely likable character into someone who seems slightly unmoored. More important, the attempt to increase the drama with fears that London will fall or the Germans will invade the U.S. aren’t necessary; there is so much real tension in other parts of the narrative.

In any case, Frankie eventually sees enough overseas and retreats to Cape Cod, where she meets Iris and Emma. The women are linked by Emma’s husband and a letter that is, for reasons I won’t reveal here, deeply meaningful to all three.

It is, perhaps, the middle third of “The Postmistress” that is most poignant and authentic and, I believe, gets at the heart of Blake’s intention for this novel: the idea that Americans were not paying attention between 1933 and 1941. In this section, Frankie travels on trains across France in 1941 with Jewish refugees trying to reach Spain or Portugal or a boat west to the Americas. Frankie is using a recording technology, Blake admits in an author’s note, that wouldn’t have been available to her for another two years, but her interviews with the families are profoundly affecting, and the tension is riveting as each visa is checked. The stakes are high for these refugees, and here the novel soars.

Of course, Blake is absolutely right: All of Europe and the U.S. should have been paying greater attention from the moment Hitler came to power in 1933. As a globe, we would pay for the fact that we failed with the cataclysmic horror that marked World War II and the Holocaust.

And that is a legacy that is truly “monstrous and horrible.”