Necessary Evil

The satisfying third volume of Tregillis’s Milkwood Triptych successfully throws time travel into a mix that already included alternate history, spycraft, and mad science. Following the events of The Coldest War—with the other-dimensional demons called Eidolons, “the mortar between the bricks of the universe,” ready to destroy the world—sociopathic clairvoyant Gretel hatches a plan to send secret agent Raybould Marsh back in time to protect humankind. Landing in 1940, an older, scarred Marsh manipulates his younger self, his young wife, and novice wizard Will Beauclerk into courses of action that often parallel those of the first book. Naturally, complications ensue thanks to the new timeline’s own manipulative Gretel and Marsh’s younger self, just as stubborn as always. Tregillis neatly juggles two viewpoints from the same character (giving the future Marsh first-person narration), and plays with notions like free will and irony while wisely avoiding headache-inducing paradox discussions. He also keeps the tale grounded in its espionage roots, providing a thrilling spy novel as much as a science fiction story. (Apr.)