The schizoid daughter of America?s most prolific serial killer, must assist the FBI in catching the man who has begun reenacting her father?s murders.

More randomized thoughts:

>>>The coldness, detachment, the apathy related to it will make it interesting

1] Have you checked out borderline personality disorder (BPD)? If you want “interesting”, BPD is the disorder of choice.

2] Whatever you choose, one complication could be that she goes on and off her medications. (Which the mentally afflicted often do because they don’t like the side affects. Or because they are indigent — can’t afford the meds on a regular basis. ) And when she’s off her meds, she’s bouncing off the walls, acting out her symptoms in extremis.

3] For those into Jungian/Campell archetypology, she could be a combo: hero + trickster. She’s the only friend she’s got — and her own worst enemy.

Well….

In order to find relief from her own demons, the schizoaffective daughter of a notorious serial killer helps the FBI to catch another serial killer who is copy-catting her father?s sadistic methods.

Problems/issues:

You have to assume no one is going to know what “schizoaffective” means. They are going to confuse it with schizophrenia. Or any other clinical term. So, I’m tempted to suggest “mentally disturbed”.

‘another serial killer’

I selected that phrase because how do they know it’s a man? Could it be a woman? (In terms of crime data, the very long odds are that it’s a man. But if you can construct a credible final twist/reveal that it’s a woman, that’s a definite plus factor in the plot to my demented way of thinking.)

‘find relief from her own demons’

In real life (as opposed to reel life)–not likely. Gone are the days when films purvey the Freudian notion that ghosts of past trauma can be exorcised by talking or some other therapeutic method. So WHY she gets involved — what her final subjective goal is — may need some thought.

But it is credible that she could be lucid enough to realize from, say, watching news stories on the TV that a serial killer is copy-catting her father’s m.o. — realizes it before the FBI does.

And, of course, if you go with that angle, they don’t believe her at first — she’s a “nut case” after all.

Potential:

On the basis of what I have read and observed of psychological disorders and psychopathology, I think it’s an interesting premise to make the protagonist a person afflicted with a mental illness.

But it’s a challenging one. Best wishes with your concept.