Korgh, protege of the long dead Klingon Commander Kruge, has seized control of the House of Kruge while working to unravel the Klingon Empire's long alliance with the Federation or at least move the Empire to leading the alliance of the Khitomer Accords signatories. He has unleashed the Unsung, a colony of disgraced Klingons whose core are the families of Kruge's discommendated military allies armed with the Birds of Prey of the Phantom Wing, a secret squadron created by Kruge and equipped with the most advanced technology Korgh's agents can discover. Led by Buxtus Cross, a member of the interstellar group of con artists known as the Circle of Jilaan, encountered by the Enterprise-D in The Next Generation episode Devil's Due, who has disguised himself as a gravely wounded Kruge, the Unsung are prepared to seek vengeance against the Klingon Empire.
The book opens by showing how Cross was recruited by the Circle. After this it shows the commissioning of a new Bird of Prey commanded by Korgh's grandson with Admiral Riker and General Kersh. But the ceremony turns into a battle when a pair of discommendated workers, inspired by the action of the Unsung, strike. A rash of attacks by other discommendated Klingons and attacks on them ensues while Riker continues to arrange talks between the Khitomer Accords signatories to negotiate a free flight path through the territories of the various powers.
But doing so will require the support of the House of Kruge, which controls much of the Klingon territory in the proposed free flight path. Korgh insists on choosing the Klingon Empire's lead representative to the conference, deliberately choosing someone who will hinder the talks, and holding them at the Spirit's Forge, a legendary Klingon Fortress guarded by an equally legendary order of warriors replenished after being wiped out during the final Borg invasion. Korgh also orders the Unsung to destroy the conference.
Meanwhile, Cross has been directing the Unsung against a series of Orion pirate hideouts seeking treasure and his Orion apprentice Shift's vengeance against her own people. Cross had been ordered by Korgh to execute the clone of Kahless the Unforgivable but instead keeps the clone alive for study, planning to someday impersonate the reincarnation of Kathless himself. He uses his Kahless impersonation to lure the defenders of the Spirit's Forge to their deaths and allowing the Unsung to take their place. But the ambush is discovered and the Unsung are driven to retreat in the ensuing battle.
I give this book 8 out of 10. The story is interesting and I enjoyed the few battle sequences a great deal. The ending also did a great job of leaving me wondering what will happen in the final book of the trilogy. However, there is a major plot twist that I feel had no real foreshadowing at all and another part where a character's actions make no sense to me given what is known of that character's culture.