A fascinating novel about love, class, loyalty and money, "The Beach at Summerly" moves deftly between post-World War II Connecticut and Massachusetts about 10 years later.

Emilia Winthrop's family has lived on Connecticut's Winthrop Island for generations, but despite the fact that the island is named for them, they are not wealthy and they are not upper-crust. Emilia's father is the caretaker of Summerly, a mansion owned by the Peabody family. Emilia grew up playing with the Peabody brothers, but since the war everything has changed. Emilia is now a young woman, the boys are war heroes and their glamorous Aunt Olive has arrived to live in the Summerly guest house.

Olive takes Emilia under her wing, hiring her to babysit her children and urging her to abandon her ailing mother and move to the mainland, for college.

Over time, it's clear that things do not add up: Why does Olive disappear into her attic most days? Why does an FBI agent come out to the island? What does he want from Emilia?

Beatriz Williams' novel is steeped in big houses, sand, surf and sunshine, and also in the darker world of war, traitors and espionage. The scenes that flash forward to 1950s Connecticut might confuse you at first, but they're meant to. Stick with it. You won't be sorry.

The Beach at Summerly

By: Beatriz Williams.

Publisher: William Morrow, 368 pages, $30.