From Goodreads:

On a midsummer weekend, in a country house in upstate New York, three friends gather on the anniversary of the death of a man related to them all by blood or love. Their idyll is disturbed by the presence of two outsiders: a faux Italian dinner guest and a young gay man now involved with the dead man's lover. As the weekend unfolds, with its walks in the woods, its swims in the river, its wine sipped by moonlight, and its sparkling conversation, each character's heart and soul is stripped bare, as old memories and new desires create a chemistry that will leave none of them untouched or unchanged.