Wow, where to begin...following on the heels of the last entry A Thousand Sons, this one features a very clever concept that really brings the Horus saga further into immediate focus. On Terra (Earth), there exists an assassination guild that operates on the fringes of the Emperor's rule. Spread among this guild (officially known as the Officio Assassinorum) are various groups known as clades, which each feature a specific expertise in the art of assassination. Chief Custodian Valdor, a high ranking official in charge of guarding the Emperor, persuades the guild to put together a team of assassins with one goal: terminate Horus and end the traitor's rule. They set out to do so, not knowing that Horus has released a chaos-infected assassin of his own to infiltrate the Emperor's inner circles. What follows is an outstanding tale of of the two opposing factions eventually crossing paths on Dagonet, realizing their efforts have been deflected, and each must destroy the other to save the very side they are working for. Faster paced than most Heresy novels, and Swallow does an outstanding job of describing and bringing to life the individual assassins and the vile, disgusting Spear, Horus' warp-possessed agent. The ending was also a jaw-dropping moment which points to future Heresy tomes..