The Hydrogen Sonata

Amid preparations though, the Regimental High Command is destroyed. Lieutenant Commander (reserve) Vyr Cossont appears to have been involved, and she is now wanted - dead, not alive. Aided only by an ancient, reconditioned android and a suspicious Culture avatar, Cossont must complete her last mission given to her by the High Command. She must find the oldest person in the Culture, a man over nine thousand years old, who might have some idea what really happened all that time ago. It seems that the final days of the Gzilt civilization are likely to prove its most perilous.