The special-ops trained scientists of Sigma Force battle the criminals of the shadowy Guild in bestseller Rollins's lively third Sigma Force thriller (after Black Order). An ancient and deadly plague, the Judas Strain (which afflicted Marco Polo), has suddenly re-emerged. Gray Pierce, a Sigma operative, and Seichan, a Guild defector, pursue clues to the nature of the plague to the Vatican, Istanbul (with a fine shootout in the Hagia Sophia mosque), Marco Polo's tomb and, finally, Cambodia's Angkor Wat. Meanwhile, Guild members hijack a cruise ship full of plague victims (to provide experimental subjects for the weaponizing of the plague), and Gray's parents are taken hostage (though the senior Grays prove feistier than their kidnappers reckon). Sophisticated the plot isn't, but Rollins includes more than enough action and suspense to keep readers turning pages. 8-city author tour.