In this story, after a team comes back from a "Spacelab" orbiting Earth, several more duplicates of the same people signal that they are returning as well. The first mystery is where they came from -- and then, what alien techology did they unwittingly bring back? They also bring back three aliens who have been sharing low rations of their own on the orbiting lab. Where did THEY come from? The newcomers inform the authorities that the lab is now packed with alien artifacts. The U.N. and various prominent countries wrangle about who should get access to alien artifacts on the space lab. Other groups argue that the aliens are angels or devils. Will the authorities go back to space and bring the food that the aliens need or will they question them to death first? And who's coming next? Heinlein would have made this come alive. For Pohl, it just plods. The book ends in a cliff-hanger, so if you care you can get the last book in the series to find out what happens next.

To be fair, this book is the second in a series and I have not read the first book. However, the characters failed to engage my interest and I struggled to finish it. Pohl seems to be a better science writer than science fiction writer. His boxed "news items" and theoretical asides seem to have more of his interest. At the end, the climax of the book seems to be delivering a lecture on tachyon theory and virtual subatomic particles. Two documents, one about the exciting developments in physics and one about diverse people dealing with aliens from space and a possible invasion by immmensely powerful and contentious "Beloved Leaders," would have worked better. ( )

Several people return to Earth after a trip to a "deserted" space station with their memories blanked. Soon duplicates of them and some aliens come back too. They must fight an alien invation.