SOLVED. Adult Serial Killer Mystery. Guy who has a history of stalking women married a girl whose sister was killed. He used to own a tech company but sold it so all he does now is dig up bodies and report them to the cops.

[Lina]

I remember that the mom opens up a clothing store that she names after her dead sister. The guy keeps like a digital journal of all the bodies he has dug up. It is the 20 year anniversary of his sister in laws murder. He is buying info from the cops but the cops dont know it is him finding the bodies. The cops end up suspecting him of the kidnapping of his daughter but after he finds her he manages to pin everything on someone else.

[Lina]

Its called find you in the dark. I figured it out

[Bargle]

Link Find You In The Dark by Nathan Ripley.