Coincidence? Spoiler Alert

Was the similarity between the abduction/rape of Catherine Gagnon and the murder of the 6 girls a coincidence or was it somehow related? It seems that the choice of Catherine Gagnon as a victim by Umbrio had nothing to do with her features; It appears to be just a red herring (pun intended) and that the two crimes were unrelated.

The only thing that seems to link the Catherine Gagnon crime to the 6 girls is that Annabelle resembles Catherine. Unless I missed something, they were not able to identify the remains to find out if they had similar features.

It seems too contrived that Catherine, Annabelle and the au paire all had similar features (red hair, blue eyes, pale skin). To have two patients at the same hospital AND who were serial killers AND friends AND to have the same attraction to red haired women...I find too far fetched.

So it seems as though there was no link between Charlie Marvin (aka Christopher Eola) and Uncle Tommy (aka Ben aka Benji) EXCEPT that they resided as the same mental hospital at the same time and had the same attraction for red haired women.

Charlie said something before he died about finding the bodies in the pit, but am I correct in assuming that he was not an accomplice of Uncle Tommy and that Uncle Tommy acted alone in killing those 6 girls over the years as a substitute for Annabelle?

If Uncle Tommy acted alone, then the subplot regarding Eola's affection for red haired women was just to keep us guessing. And if he acted alone, why did Charlie Marvin show up at Annabelle's apartment with a knife?

They never really explained how or why the killer abducted and killed Dori Pettracelli. She wasn't a redhead and no explanation was given for how he found her in another town.

They also never explained the questionable circumstances surrounding the fire that killed Annabelle's father.

I could read the book but from other reviews it appears that the storyline was changed so it would not help clear up the loose ends of the movie.