Starlight on Willow Lake / Susan Wiggs.

Enhanced descriptions from Syndetics:

#1 New York Times bestselling author Susan Wiggs sweeps readers away to a sun-drenched summer on the shores of Willow Lake in a stunning tale of the delicate ties that bind a family together...and the secrets that tear them apart

When caregiver Faith McCallum arrives at the enchanted lakeside estate of Avalon's renowned Bellamy family, she's intent on rebuilding her shattered life and giving her two daughters a chance at a better future. But she faces a formidable challenge in the form of her stubborn and difficult new employer, Alice Bellamy. While Faith proves a worthy match for her sharp-tongued client, she often finds herself at a loss for words in the presence of Mason Bellamy--Alice's charismatic son, who clearly longs to escape the family mansion and return to his fast-paced, exciting life in Manhattan...and his beautiful, jet-setting fiancée.

The last place Mason wants to be is a remote town in the Catskills, far from his life in the city, and Faith McCallum is supposed to be the key to his escape. Hiring the gentle-hearted yet strong-willed caregiver as a live-in nurse gives his mother companionship and Mason the freedom to return to his no-attachments routine. For Faith, it means stability for her daughters and a much-needed new home. When Faith makes a chilling discovery about Alice's accident, Mason is forced to reconsider his desire to keep everyone, including his mother, at a distance. Now he finds himself wondering if the supercharged life he's created for himself is what he truly wants...and whether exploring his past might lead to a new life--and lasting love--on the tranquil shores of Willow Lake.