Matter : [a Culture novel]
(Book)

In a distant-future, highly advanced society of seemingly unlimited technological capability, a crime is committed within a war. For one brother it means a desperate flight, and a search for the one--maybe two--people who could clear his name. For his brother it means a life lived under constant threat of treachery and murder. And for their sister, it means returning to a place she'd thought abandoned forever. Only the sister is not what she once was; Djan Seriy Anaplian has become an agent of the Culture's Special Circumstances section, charged with high-level interference in civilizations throughout the greater galaxy. Concealing her new identity--and her particular set of abilities--might be a dangerous strategy. In the world to which Anaplian returns, nothing is quite as it seems; and determining the appropriate level of interference in someone else's war is never a simple matter.--From publisher description.