I Know What You Flushed Last Summer(2001)
(The fourth book in the Fright Club series)
A novel by Chris Archer
There are lots of unpleasant things about the bathroom. But none of them could compare to the terrifying creature that just crawled out of 12-year-old Ellie's toilet. It smells bad and it looks even worse! Now Ellie's running all over New York City trying to escape this science experiment gone wrong and, unless she can come up with a plan to stop the sewer monster, it's her life that might get flushed!
August 2001 : USA Paperback