From what I remember: Main character is a young mentally troubled male working at a small insurance/telemarketing type company. Has one friend who is a co-worker (his boss I think?), lives alone, he greatly enjoys jazz music and painting.
Pretty girl starts working there, she starts talking to him, they connect. She finds sketches of other girls in his bedroom, infers that he knew all these girls previously and possibly killed them. They struggle and I think the scene fades to credits?
I cannot remember the name of this for the life of me, and I haven't seen either person in any other films.