In a twisted story of co-dependence, two sisters are pitted against each other by a giant, abhorrent leech creature that uses its mind-controlling influence to puppeteer them from the inside out.

A young woman survives a great white shark attack, whilst on a family boating vacation, however soon realizes the nightmare is far from over. Those around her can not be trusted, and she must face her demons, if she is to step back in the water.