two years after haley's birth, she decided to invite 16-year-old foster child, sabrina zunich, into her home. and to make sabrina part of the family. >> everything was going really well. she fit right into the family. lisa couldn't talk highly enough about her. >> but the happy times for the knoefel's blended and extended family would end catastrophically on that november night back in 2012 when lisa knoefel was brutally stabbed in her home. >> when i heard it was lisa and who did it ... i can believe it. it was like, you are kidding me. >> a devoted mom attacked and her own home, enough to stun any family. but a crime this vicious? the first responding officers arrived at a frantic scene. coming up. >> the blade was actually bent. i just are shaking my head. i couldn't ... it takes a lot to bend a knife blade. >> one deadly betrayal continues. what can i du with less asthma? with dupixent, i can du more.. catching my train... making moves... ♪♪ making a connection... a train connection. that's how you du more with dupixent, which helps prevent asthma attacks. dupixent is not for sudden