On a planet alien - Barry N Malzberg

SCOPis the tale of a time traveller trying to stop some of history's worst moments before they happen. He has witnessed the last minutes of Jack Kennedy, King, Malcolm, Robert Kennedy. But Scop, in trying to alter, has merely reinforced the future. In the ENCLOSURE is the story of Quir, an alien forced to endure endless interrogations following the first meeting of creatures from space with the people of Earth. An alien whose only thoughts are of escape. For those arriving ON A PLANET ALIEN, the mission was to educate the native inhabitants of Folsom's planet and bring them withing the Federation. But something had happened on the voyage there. Could it be start some unknown force was controlling the crew's minds, a force that could bring disaster to the mission?