I am looking for a book which came from a public library, I read it about... 15 years back, I believe. I cannot remember the title of the book nor the author, but I remember some of the plot.
Humans have developed FTL travel by making a large mothership "attune" to a distant planet and then slingshotting there; A group of people investigate a new planet and capture an alien, which they think is just an animal, but turns out to be a member of the dominant, sentient species on the planet, the alien is sort of a bat-like creature with leathery sails between its arms that allow it to fly, but it is enhanced by advanced technology, some bio/cyber augmentation of filaments in the wings that allow it to locally control gravity.
On the way back to earth, they discover that the alien is highly intelligent, being able to reproduce nearly all sounds, which it uses to open its cage by fooling a voice recognition lock, and also learns the language of its captors.
On earth, they actually befriend the alien as they discover that he is sapient; He later tells them his name, which is something along the lines of "Shadow in the center of the flame" Which they then abbreviate to just "Shadow". I'm pretty sure that he was also able to use telepathy, and later in the story he is also shown as an empath, as he can read facial expressions and things like that.
They are members of some secret society that is somewhat against the government, and they have made plans to leave earth, at some point, and decide to introduce the alien to their society, and later escape with him to his home planet. To do so, they have to purchase a lot of items they brought back from the planet, as in order to get back to a specific planet, you have to have some mass aboard your ship that is attuned to that planet, because it came from there.
Can you tell me the book's name? Help would be much appreciated, I have already spent a couple hours looking for it myself! Thanks in advance.