Recipe for (suspense plot) Confusion
When you start considering one plot scenario and an exciting twist occurs to you, and then another, and you start twisting things around until you wind up with something like a baseball game with several teams and about 10 bases. Oh, and something like four home plates.
Recipe for (in this case, suspense/crime) plot confusion:
original death premise
kill witness option
take neighbor hostage option
him see her meet another man option
That's all before adding a pinch of plot resolution and a dash of interesting but conflicted characters. Stir well and read!