you doing blank like that is why i will never completely trust you. later that night, skylar is seen here on that surveillance tape driving away from home for the last time. what were they fighting about? there's a possible answer. hallway whispers that rachel and sheila had developed a sexual relationship and that skylar knew and threatened to out them. did they kill her to keep their secret? it's as close to a motive as anyone can come up with. >> do you think we'll ever know why this happened? >> i think that's something for rachel and sheila to say. they know the answers to that. >> in january 2014, dave and mary finally got the news they had been hoping for, a plea deal. >> sheila eddy, how do you plead to the offense of murder in the first degree, the felony charge in count three of the indictment in this case? >> guilty. >> sheila's attorney michael benninger read a statement from sheila and her family.