Escape Attempt
Boris Strugatsky
 The novel tells a story of two young men from Earth, Anton and Vadim, who decide to go for a trip to Pandora, but are persuaded rather to travel to an uncharted planet by a mysterious man whom they know as Saul Repnin. Their choice is an unnamed planet in EN-7031 system, because that's where Gorbovsky and Bader predicted that Wanderers' traces could be found. After landing successfully on the planet (which they named Saula after Repnin), the explorers soon discover a local human civilization, as well as the predicted Wanderers' traces. The latter appear as a phenomenon later called "everlasting machines" and largely influence the entire local population. Despite the fact that it is strictly forbidden for them to initiate a contact with any human or alien civilization without an authorization from COMCON, they try to do just this - and fail, having misinterpreted the situation. What they see as catastrophic is just a routine life in an early feudalistic society of Saula. Saul Repnin, who, as it was later uncovered, was a prisoner in a Nazi concentration camp but shifted into the future (s.c. time guest), is so shocked to see a local civilization (even though it's not the Earth's one) commit just the same cruelties he saw in his time, that it causes a severe psychological crisis in him. Anton and Vadim decide that it's the best to leave the planet immediately and after they arrive back on Earth, they discover that Saul has disappeared, leaving a short note, which partly explains who he was and that he wants to go back. Saul Repnin was killed soon after he returned to his time.