My Plot.

Perhaps this would be better suited to the Sandbox?

Brayden! Good to see you.

Did you have a question, or were you introducing yourself?

Don't worry, the forum gets easier to navigate with time.

Welcome, Brayden. I think this belongs in the Sandbox. A mod will likely move it on request.

I think there are important bits missing from your summary -- what case is he involved in? How does it put him in conflict with his relationship? What makes him snap and why when he snaps does he kill his girlfriend and her lover?

Welcome Brayden!

Yep, this should go in the Sandbox. You might like to add some more information along the lines of what Ruv suggested, so that people can get more of an idea about the story.

Remember that the majority of the appeal comes from the characters, so make sure you express what kind of people we're dealing with, what are their ruling passions, their flaws, their backgrounds, their talents, and their self-images?

I'm wondering if that's the starting point or your ending. If it's a starting point, then I'm pretty darn intrigued and that sounds cool. If it's the ending, then I'd say it depends most on the character that you've created. My initial reaction is that if I read a book and liked a character and at the end he just snapped and killed people, I'd probably be a bit irritated with it. Though I also tend to like dark books and what not. If it's clear that he's got issues and there is a good enough motivation (I think it would take more than just job stress, perhaps the case itself is incredibly personal for him somehow) then it would probably be okay, however.

Do you know more, or is this just batting around without detail in your head still?

This is more of a plot point than a plot. You need to flesh it out a bit more before you can get much help on the full storyline.

You've got character traits (the obsessiveness and haunted aspect), but there's no frame of reference for them. What - exactly - do you mean by obsessive? Is he putting in long hours? Hounding people he assumes are guilty, even if they're not? What - exactly - do yo mean by haunted? Was there a family that he lost to a case and he feels guilty about it, and therefore driven? Did he do something terrible in the past? Did he railroad an innocent person and feels guilty?

You say he kills his girlfriend and her lover, but is this a current girlfriend? Did she leave him because of his personality/work habits? Is he stalker-like and didn't get that it was over, or was the girlfriend always seeing this guy on the side?

Is the murder the climax of the story or the inciting incident? What happens to him as a result of the murder? Is this a redemption story or just the journey of a once good man slowly unraveling? Was he never a good man, and had barely managed not to cross that line before?

You have the beginnings of a story, but you've got a bit of groundwork to do before it's a full plot.