Gathering Prey finds Lucas's adopted daughter Letty kicking off the action by befriending some homeless-by-choice folks she meets at college. Later, when one of those people is in trouble, she calls Letty for help and Letty brings Lucas along. At first skeptical that anything's wrong or that he's getting anything like a straight story, Lucas looks into things as a favor to Letty. Before long, he finds her friend's suspicions are on target. But they're only the tip of a malignant and murderous truth that will endanger Lucas and his family, as well as perhaps sending him too far over the line at his job with Minnesota's Bureau of Criminal Apprehension to come back.
As mentioned above, Gathering doesn't so much present a mystery to solve as a target to hunt. The evil Pilot and his crew owe more than a little to the Manson Family, and the story centers on overcoming Lucas' initial reluctance to believe they exist and then on tracking them down before they kill too many more people. That part of the story isn't very new, even to Sandford, who sent BCA investigator Virgil Flowers on a similar race-the-clock hunt for a kill-happy couple in 2012's Mad River.
More interesting is the interaction between Lucas and Letty, as Sandford begins to craft her as a character on her own rather than just scenery in the Davenport home life. It seems clear that at some point the author would like to hang a few books on Letty if possible and may be testing out a good voice to use in writing her. Also of some interest is Lucas' increasing tension with his political overseers. Already impatient with fools and made even more so as the body count rises and his supervisors try to cover their own behinds first, Lucas may have to walk completely outside the lines in order to bring his prey to ground, and there's no certainty he will be able to come back if he does. Those factors set Gathering Prey a little ahead of the pack of the series and prompt some anticipation about its future direction.
Along the way, Her Highness Princess Kristine Longknife of the United Sentients has crossed paths with Grand Duchess Victoria Peterwald of the Greenfeld star empire on a couple of occasions, most notably when Vicky tried to kill her in revenge for her brother's death. Their last encounter, though, helped Vicky to learn that Kris wasn't responsible for that death, and she might have to take matters into her own hands to bring down the culprit. But she's a Peterwald female, trained to be a good lure for her father to dangle as marriage material in the interests of his own political ambitions. She's got a lot to learn about how to handle things on her own and little time to do it.
Shepherd began the Vicky Peterwald series with Target, which set up the situation our Grand Duchess finds herself in, and continues with Survivor. Her opponents move openly against her now, and their aims both where she is concerned and on a larger scale become clear. So does their cost, as Vicky finds herself first saddened and then enraged by the disregard shown for innocent bystanders. She uses both, as well as the lessons in responsibility taught her in the Greenfeld navy, to begin to live up to the responsibility her powerful position implies.
Survivor is immensely better than Target, in which Shepherd seemed to indulge just about every adolescently snickering sexual single-entendre he could dream up while describing Vicky's initial run for safety, It also wastes much less narrative on dead ends, and begins solidifying her character arc as she tries to shed the humiliating expectations of her palace upbringing in order to find what kind of human being she wants to be.
Shepherd's not exactly a deft enough writer to distinguish Vicky from Kris within the narrative; he usually has to make an explicit comparison in some character's words or Vicky's own internal dialogue (part of his reason for all of the bedroom romping in Target may have been a clumsy and very icky attempt to draw that distinction). But he does so fairly well within that limitation, not stopping the flow and he makes Survivor enjoyable enough that a space-opera fans could put the next Vicky Peterwald book on their buy lists. Which was nothing like a sure thing after her initial voyage.