The crack, ultrasecret Sigma Force team returns in another adventure that, as usual, unfolds at breakneck speed. Sigma Force, made up of former Special Forces officers trained as experts in various scientific fields ("killer scientists," one of their number calls them), scours the world for technologies that could help or threaten the U.S. This time the group's mission involves a devastating bacteriological plague, a mysterious cryptogram that may predate humanity, and the deadly truth about what happened after Marco Polo's expedition to China. After a handful of Sigma Force novels, Rollins has fine-tuned the formula to precision: characters rendered in broad strokes, punchy dialogue, short paragraphs that propel us headlong through the story. The novels are like prose versions of comic books, or lightly fleshed out movie treatments. But this is not a criticism, at least not completely. The books' style perfectly matches their subject matter, and it's impossible not to be swept up by their energy and excitement. Action/adventure fans unfamiliar with Rollins' work should be emphatically urged to read this series.