Could someone ever forgive a mom who would abandon not one but three newborn babies within blocks of each other over a five-year period? It is an incredible mystery that is solved right before viewers' eyes, as "20/20" teams up with renowned DNA detective and genetic genealogist CeCe Moore. Janet Barnicoat, one of those three baby foundlings, started her search as many do, with a Facebook post begging for clues about her biological family. The post went viral. After hearing about her story, Moore volunteered to help her on her search. What followed is a bewildering and shocking story, as Barnicot discovers she is one of three siblings abandoned by the same mother. But once the three are reunited, they go on a quest to find that mystery mom responsible for the unthinkable. It all culminates in a dramatic family confrontation and a series of startling confessions. Even Moore, with her 16 years of experience, had never seen a story like this one – telling Elizabeth Vargas, "It just blew my mind."