Is it implied...
That Prendergast's wife may have kills their daughter?
Stay with me here. Prendergast said to Bill that his wife didn't want a child. He said she sacrificed her body to make him happy. He tells him she died of SIDS but it was very strange because she wasn't a baby, she was four years old.
Furthermore, Prendergast's wife is clearly mentally unstable. We know this from her behavior in the film as well as the anecdote he tells his partner about how he came home late from work one night and she was convinced he had been killed in the line of duty and was a ghost. He had to chase her around the house.
Did anyone else pick up on this?