Stickyandhotfromthelongdrivetovisitarelativeattheirnewlyacquired,remote,ruralfarmhouse,SamandJason,ayoungcoupleonvacation,decidetoswiminapondtheyfindattheendofafreshlycutpath.Whileswimming,Jasonisbittenbyastrangeleech-likeorganism.Whenheattemptstoremovethecreature,partofitripsoffandcrawlsinsidehisleg.Backatthehouse,Samssisterandherfamilyhaveyettoreturn.Astimeprogresses,theinjuryonJasonslegworsensintoarapidlyspreadinginfection,andstrangecluesbegintorevealthattheremaybemoretotheirhostsabsencethanitpreviouslyappeared.ItsoonbecomesaraceagainsttimetodiscoverwhathappenedtoSamssisterandherfamilyandwhatliesinstoreforJason,facedwithhisphysicalandemotionaldisintegration.