A sea monster, terrible with its snake-like appearance, rises from the deep water, then vanishes into the great depth of Spirit Lake. Sheriff Jeff McQuede is called in to investigate the death of Evan Spence, multi-millionaire and owner of Spirit Lake Resort, recently found dead when his boat crashed into rocks. Instead of leaving his vast fortune to his son, Oliver, Spence has formed a trust which includes seven members. Spirit Lake has long been rumored to be the home of a mysterious lake serpent fondly called Jessie, which is similar to Scotland's infamous Loch Ness Monster. The trust members are vying for control, with half of them wanting to capitalize on the Jessie legend, even to the point of building an amusement park, but meeting with adamant opposition from Oliver Spence. After a new Jessie sighting is reported, people swarm to the Spirit Lake Resort, yet when a second mysterious drowning occurs, fear abounds, and they leave in droves. Is the serpent real, or is someone using Jessie as a sinister tool of death to gain control of Spirit Lake?