Trudging to Eden — Kim Antieau

Erin Ryan is hired by a rich and powerful woman to find her kidnapped genetically altered son, Benjamin Grey, who can “sing like an angel.” Ryan and her partner Walker are soon tracking Benjamin across the galaxy. As they get closer to finding him, Ryan begins to wonder if Benjamin Grey might be the cure she's been seeking for all of her life. (This short story first appeared in The Magazine of Fantasy and Science Fiction.)