Secret super people

Question

I'm trying to recall the details of a sci-fi book I read a while back. The story involves an Erath secret police organization that investigates "Unexplained Events" or UEs. Through their investigation, they come to believe they are witnessing the actions of a precursor civilization. However, they eventually discover the UEs are actually caused by a secret society that claims to be a distinct species of humans with advanced mental powers. This group routinely conduct experiments on regular humans and manipulates them to find more members for the group.

Then I recall that one of the main characters, a secret police officer has the potential to join these superhumans themselves afterwards, contact is lost with this character, and the story is framed as a memoir from another character trying to shed light on what happened.

Does this ring a bell for anyone?

Answer 1

Is it possible you're remembering The Time Wanderers (English 1987, original title Волны гасят ветер 1986, alternate English title The Waves Extinguish the Wind, 2023) by the Strugatsky brothers?

Quoting the plot summary on Wikipedia:

The principal characters are Maxim Kammerer and Toivo Glumov, both working for an organization which investigates "Unexplained Events" (UEs). Their investigation of a series of events leads them to believe that they are witnesses to a new action by the precursor civilization of the Wanderers.

After much investigation, the UEs are discovered to be the work of a secret society called the Ludens. They claim to have chosen this name for themselves as a derivative of the Russian word lyudi "humans", "people" with several semi-jocular allusions such as the popular Latin phrase Homo Ludens "the Playing Man" and an anagram of the Russian word nelyudi "inhuman people" (as they believe they are regarded by some "ordinary" humans). The Ludens are born human, but possess latent mental powers far beyond those of normal humans. They view themselves as a distinct species, and claim to have "different interests" from humanity at large, in some instances claiming to be above traditional human morality. The Ludens routinely conduct experiments on humans and alter their minds in order to further their own means.

Kammerer and Glumov's investigation unmasks the Ludens, and they are made public in what would later become known as "The Great Revelation". It turns out that Glumov possesses this capacity, and must now decide whether or not to become a Luden himself. He at first states that to join the Ludens would be a betrayal of his family, friends, and human civilization. But he decides to try it out, if only to serve as Humanity's "ambassador" with them. Soon all contacts with Glumov are lost, Kammerer hypothesizing that he "just forgot about us now". Indeed, the story is told as Maxim's memoir, his sole intent in writing it being to clear up the story of Glumov: another source (in the fictional setting) had implied that Glumov was in the Luden group all along.