THE TWENTY-THREE by Linwood Barclay

I enjoyed this book.  There were almost too many plots; I sometimes had trouble figuring out which plot they were discussing.  I was very surprised by the perpetrator of the poisoning. I hated the ending. It was left wide open. But I did enjoy the book.  The Promise Falls police department were looking for the person who put poison in the water supply and in the act killed the man on duty and  over 200 people.  During this whole investigation, a woman at the town college is found dead.  This death seems to be that of a serial killer who has killed two women before.  And an inmate has escaped prison.  The ending of some of these mysteries is not even in the story.  I did not like that.