So what's under the water in that lake deep in the Maine woods? No one is sure what it could be, but a dead and severely mutilated body was found near the shore, and the only clue is a large tooth which appears to be from a prehistoric animal resembling a huge crocodile. Jack Wells (Bill Pullman), the local fish and game warden, is investigating the case when he's assigned a helper, paleontologist Kelly Scott (Bridget Fonda). Kelly generally does office work since she hates the outdoors (a drawback in her line of work) and is recovering from a breakup with one of her co-workers. Jack would just as soon handle this matter without Kelly's help, but with time, the two get used to each other and something beyond a working relationship begins to develop. Meanwhile, Jack and Kelly also have to deal with Sheriff Hank Keogh (Brendan Gleeson), who would like to find the mystery creature and kill it; Hector Cyr (Oliver Platt), a quirky mythology expert who wants to capture and study the beast; and Mrs. Bickerman (Betty White), an eccentric older woman with dubious stories about her missing cattle -- and missing husband.