Underwater they waited, their thirst for blood running deep.
Soon… very soon, they would feed again.

Determined to fix their troubled marriage, Cat and Leif purchase a summer home on an idyllic lake, hours away from their hectic city life. While Leif is working, Cat keeps busy by spending time in the water or visiting with new friends, who warn her about the urban legends of the lake. Curious, Cat digs for more information, discovering a trio of mysterious deaths a century ago, and a woman who claimed the weeds to be responsible.

One drunken night, she makes a horrible mistake, widening the fissure in their marriage. Trying to figure out where it all went wrong, Cat finds comfort in the water. But soon, the betrayer becomes the betrayed as Cat slowly learns the truth about that night, and the weeds once again seek justice for the one who was wronged.