Harry Turtledove 
Noninterference [EPUB ebook] 

When the Survey Service first came to Bilbeis IV, it found a planet inhabited by humanoid aliens just on the verge of civilization. Then compassion overcame common sense, and David Ware did the one thing the Service prohibited – he interfered. Just a little. But when the Survey Service returned 1, 500 years later, it discovered just what David Ware’s meddling had done. The bureaucrats of the Survey Service could not afford to allow just a breach of Noninteference to be publicized. So they set out to cover it up. Reports were destroyed, files erased, and people eliminated. For the future of the Survey Service was at stake – and so was the future of Bilbeis IV.