The Dark Twin

From Author Wars - https://authorwars.com/publications/the-dark-twin-443240.html

Overview:

Title: The Dark Twin
Author: Marion Campbell
Year: 1974
ISBN-10: 0841503451
Publisher: Saturday Review Press / E. P. Dutton
Price: $7.95
Pages: 254
Binding: Hardcover
Type: Novel
Title Reference: The Dark Twin
Notes:
• First US edition. Price from: https://www.nytimes.com/1974/09/27/archives/a-listing-of-recently-published-books-fiction-general.html; month (1074) from back flap of archive.org copy. Last page is unnumbered.