Lake Alban and its immediate environs form the setting for Loch, where plesiosaurs are trapped almost by accident. They have lived hidden for geologic eras, surrounded by an abundance of food, in the deep waters of Lake Champlain. They get into trouble through their avid pursuit of the salmon that make an annual run from the sea into Lake Champlain and then upstream into the smaller Lake Alban.

A family of plesiosaurs follow the salmon into Lake Alban and are trapped when a new salmon grid is installed, a device intended to help the salmon make their way upstream but which blocks the river to Lake Champlain.

The lake itself is a dangerous place since threatening plesiosaurs lurk under its surface; the menace is made clear early in the story when the photographer Erdon is killed by the angry patriarch of the plesiosaur family. An abandoned timber mill...