Like Stars in Heaven (Siobhan Dunmoore, #3)

One last mission. One mysterious passenger. One baffling destination. After centuries of travel, an ancient log buoy finally reaches human-controlled space. In the midst of a stalemated interstellar war, the Admiralty has little interest in wasting resources on what would likely be a fruitless search for the truth, but someone was able to convince them they could afford to send an old, obsolete frigate soon destined for the scrapyard, on this quest. Pulled from her patrol route, Siobhan Dun...