A woman whose mother was murdered when she was a child of twelve, is now, fifteen years later, working as a detective and still pursuing her mother's killer, who, it turns out, is closer than she thinks.

i am just going to take the liberty: ?"when a detective receives a mysterious phone call, she dives back in the cold case of her's mother's murder."

Then shoot for a target maximum length of 30. While not the ideal, it's tolerable, permissible.

I think you have a concept for an interesting story, particularly the psychological impact off his discovery at a vulnerable age. He may be a geek, intellectually advanced for his years, but emotionally he's still only a 10-year old boy. In the gap therein lies an interesting subjective story line to complement and deepen the main story line.

Thanks for the feedback.
It sounds like my story is just too complicated to be laid out in 25 or so words.