Centers on the events leading up to the cataclysmic 1980 eruption of Mount St. Helens in Washington, with the story beginning on the day volcanic activity started on March 20, 1980, and ending on the day of the eruption, May 18, 1980.

Art Carney
as Harry Truman

David Huffman
as David Jackson

Cassie Yates
as Linda Steele

Albert Salmi
as Clyde Whittaker

Ron O'Neal
as Otis Kaylor

Tim Thomerson
as Sheriff Wayne Temple

Bill McKinney
as Kilpatrick

Redmond Gleeson
as Hendricks

Nehemiah Persoff
as Mr. Ellison

Brendan Burns
as David Crockett