Night Walk (novel)

Earth sends secret agent Sam Tallon to Emm Luther to infiltrate the theocracy and extract the coordinates of the "null-space" (hyperspace) jump points of a newly discovered colonizable world, a closely guarded secret.

A high-ranking officer named Cherkassky tries to render Tallon harmless by erasing his memory of the jump data, using a device called a "brain brush".

While he is there, he enlists the aid of the scientific elite among the other political prisoners there, and together they design a pair of electronic "sonar" eyes.

Tallon escapes and travels across the continent, reaching his secret contact after much difficulty, and with the help of his love interest Helen Juste.

He gains knowledge of the structure of null-space (a Kummer surface) that space travelers will find invaluable.

He eventually reaches home with his enemy (and some loved ones) dead, but his new knowledge helps bring about greater peace.