The Knowledge

I have a fantasy drama novel nearing completion. It is mainly first person narrative, but three third person narritive stories which continue throughout the course of the book. Culminating in a (to be continued) ending. My problem is pace, substance and most of all, setting of these three within the main story. The three subplots have to be integrated at such a point within the main story as to have an impact.
Note : Very graphic in it\'s depiction and could be controversial in it\'s subject matter. Regards David