Mark and Donnah Winger were a picture-perfect Midwestern family with a three-month-old baby. But tragedy struck when Mark said he shot an intruder who he discovered killing Donnah. The case was quickly closed, and in an attempt to move past the horrific loss, Mark started a new life and married his daughter’s new nanny. But years later, a startling admission from Donnah’s close friend cracked open Mark’s perfect façade, exposing his deadly secret. A two-hour “20/20” has interviews with Mark’s ex-wife, Rebecca Simic, and their four children, Bailey, Anna, Maggie and Ben Simic. They speak out about the perfect husband and father they thought they lived with for years and their feelings towards Mark today. “20/20” also features the interviews with Donnah’s sisters, Jenny Levin and Michelle Hansen. They open up about losing their sister, learning the truth about Mark and how reconnecting with their niece, Bailey — just a baby inside the house at the time of the murders – helped heal the pain of their sister’s loss. “20/20” also features a rare jailhouse interview with Mark, who opens up about the events leading up to Donnah’s death and includes analysis from best-selling crime author Harlan Coben.