Novice private investigator Pamela Thompson is hired by Lydia Jennings to investigate mismanagement at her palatial 'cottage' Broadmore Hall, in the Berkshires of Western Massachusetts.
Pamela discovers the butler living a double life at Lydia's expense.
Soon Pamela has to deal with a mare's nest of family problems, mostly generated by Lydia's husband, Henry Jennings, the ruthless and unfaithful Copper King, whose sole purpose in life is to become the richest man in America.
The climax comes at Broadmoar during Henry's 4th July party - a grandiose event that he personally orchestrates.
The next morning, his body is found in his study. Pamela's boss, the lawyer Jeremiah Prescott, joins her for the investigation.
Now they have to figure out, from among the many suspects, who killed Henry Jennings...