On her Christmas vacation with her brother's family, Scully receives a mysterious phone call from a familiar voice who says, "She needs your help. Go to her." The phone call leads Scully to a murder case where the victim's 3-year-old adopted daughter bears an uncanny likeness to her sister, Melissa, at that age. The emotional roller coaster that follows has Scully believing that her sister had a baby during a period when she traveled the country and she tries to adopt the child, knowing that caring for the little girl would change her life.

DNA testing on Emily reveals that she is actually Scully's daughter and Mulder comes to assist her and to find out where and how the girl was born while Scully tries to help Emily with her own serious illness, a rare form of anemia.