Bloodwater

They're all dead now. I am the last one. Dr Morrow can't identify the 'thing' he found living in the lake but he knows it's dangerous . . . then it goes missing . . . Caught in the flood that is devastating the town, brothers Sean and James stumble across Morrow and the carnage left at his lab.

The missing specimen is some kind of deadly parasite that moves from person to person, destroying its hosts in disgusting, gory ways. The death toll will rise along with the waters unless the brothers can track down the homicidal specimen and find a way to destroy it.