Endeavour - Ark Royal, #18

For generations, the human race has feared an encounter with an alien race so advanced their technology might as well be magic.  And yet, no such alien race has been encountered ... ... Until now. During the Virus War, human explorers discovered proof of alien technology that was beyond human understanding, technology so strange it was impossible even to guess at its function.  Now, in the aftermath of the war, HMS Endeavour embarks on a mission to the core of the alien civilisation ... ...
And discovers a mystery older than the human race itself.