- "When danger is uncaged, the only law is the law of survival."
- — Tag-line from front cover
Endangered Species is the first book in the Operation Phoenix Trilogy and book 64 in The Hardy Boys Casefiles. It was first published in June 1992 by Archway Paperbacks (an imprint of Simon & Schuster).
- "The killing fields of Kenya!"
- — Tag-line from back cover
The Hardy boys join their father, Fenton on an undercover mission in Africa, to investigate a multimillion-dollar smuggling ring, and discover the fate of a missing U.S. Customs official who was on the trail of the gang before he disappeared.
The poachers are killing hundreds of endangered animals, for their smuggling operation, and the Hardys determined to shut them down.
Frank and Joe discover that the Customs official was killed, and are closing in on the gang, which they have discovered is Phoenix Enterprises, when their own father is killed in a tragic bombing. The brothers discovered a clue that leads them to believe that Phoenix Enterprises is based out of Stockholm, Sweden, and they vow to go there to track down their fathers killers
- Kevin Alladyce
- Rosalyn Bodine
- Ethan Daly
- Fenton Hardy
- Frank Hardy
- Joe Hardy
- Martin Jellicoe
- Christopher Lincoln
- Indian Ocean (mentioned only)
- Manhattan, NY.
- Maryland (mentioned only)
- Mombasa (mentioned only)
- Nairobi, Kenya
- New Zealand (mentioned only)
- New York, NY.
- Stockholm, Sweden (mentioned only)
Businesses and organizations
- Bodine Animal Research Facility
- Nairobi Animal Habitat
- Phoenix Enterprises
- U.S. Customs Service
- World Trade Center
- This is the only book of the trilogy to not contain an excerpt from A Hardy Boys and Tom Swift Ultra Thriller: Time Bomb.
- This book, along with The Phoenix Equation have been out of print since February 1998. No Mercy went out of print in the early 2000s.