Infiltrator (Star Trek: The Next Generation, Book 42)

Centuries ago, followers of the tyrant Khan Noonien Singh left Earth for the planet Hera to continue his experiment in selective breeding. Now, they are finally ready to launch their plan of universal domination-- with the U.S.S. Enterprise as their weapon. Captain Picard must enlist the help of Heran expatriate Astrid Kemal to defeat her fellow superbeings. Unless the captain and crew of the Enterprise can stop them, the Heran infiltrators could alter the genetic landscape of the galaxy for generations to come.