In his novel Old Man's War, John Scalzi offered readers the tale of John Perry (the eponymous "old man" of the book's title) as he left the Earth at the end of his life and began a new one as a green-skinned soldier of the Colonial Defense Forces. While a solitary work, it also opened the door to a new universe of stories, which Scalzi began to take readers through with this novel. In doing so, he sets John Perry aside and uses two secondary characters from his first novel -- Perry's fellow recruit Harry Wilson and Special Forces soldier Jane Perry -- to tell a very different tale about the efforts by the Colonial Defense Forces to unravel a conspiracy by a human scientist to start a war between the Colonial Union and three alien races. The focus of the book is the CDF's efforts to unravel the conspiracy, which involve a combination of sleuthing, military action, and the journey of a Special Forces soldier imprinted with the scientist's brain patterns. The result is not only a worthy sequel to Scalzi's entertaining first book, but it demonstrates the storytelling possibilities of the universe he is created and his ability to do more than just recycle the same adventures in a different setting.