The Other End of Time (Eschaton Sequence)

Strange signals have reached the Earth, warning of its destruction by malevolent aliens known as the Horch. Within a year there is evidence that the aliens who sent the warning, known only as the Beloved Leaders, have taken over the Starlab, an abandoned orbital observatory. When a group of astronomers goes to investigate the observatory, they are taken light-years away, becoming prisoners and guinea pigs of the Beloved Leaders. Led by Dan Dannerman, cousin of the observatory's director and a spy for the U.S. government, the prisoners take stock of their situation and gradually discover the truth that their captors, who have told the prisoners they are at war with the monstrous Horch, are lying about their own diabolical aims. When the Horch attack the prison base, they inadvertently free Dannerman and his fellow prisoners, allowing the humans to turn the tables. The Beloved Leaders have committed the cardinal mistake: underestimating the ingenuity of their resourceful human prisoners. And they're going to pay dearly for that mistake!