The Latecomer follows the story of the wealthy, New York City-based Oppenheimer family, from the first meeting of parents Salo and Johanna, under tragic circumstances, to their triplets born during the early days of IVF. As children, the three siblings -- Harrison, Lewyn, and Sally -- feel no strong familial bond and cannot wait to go their separate ways, even as their father becomes more distanced and their mother more desperate. When the triplets leave for college, Johanna, faced with being truly alone, makes the decision to have a fourth child. What role will the "latecomer" play in this fractured family?