The Foreigner — Meg Castaldo

Alex Orlando is a foreigner in New York -- a California foreigner, housesitting for her Uncle Carmi while he vacations in Puerto Rico. She quickly becomes entwined with her attractive Swedish neighbor, Christian, but something isn't quite right about him. For instance: where does he get all that cash? Her oldest friends, Kyle, has turned into a stalked, and a much-anticipated visit from Jan, her European boyfriend, quickly turns into a nightmare.
Manhattan is a foreign landscape filled with suspects in Meg Castaldo's daring and irresistible first novel.