That Summer in Ischia

In the long hot summer of 1979, best friends Helena and Liddy travel to the beautiful island of Ischia to be au pairs to the children of two wealthy Italian families: the Verduccis and the Baldinis. From the opulent hillside villas and the sun-drenched beaches the girls plan their great adventure to find romance and excitement, whatever the cost, on the sleepy island. But when a little boy in their care goes missing the spell is broken and the girls find themselves under suspicion from the police. Under pressure, the cracks in their relationship are forced to the surface and one will betray the other, changing the course of both their lives forever.
Twenty-four years later, Liddy, walking her dog on an English beach, spies a woman strangely reminiscent of her estranged friend. Hoping for reconciliation, Liddy follows the figure home. But this isn't Helena; it's her twenty-three year old daughter, Allie, a daughter Liddy never knew about. As their friendship blossoms, new mysteries come to light, sending Allie on a startling quest to find out what really happened that summer in Ischia.

(from amazon.co.uk)