When a young researcher ventures through a mysterious planetary system, dangerous secrets come to light in this novel from a Hugo Award-winning author. Grad student Danae Panya's dream assignment has been approved. She'll study Triplet, the strange planetary system scarred by nuclear war and connected through portals. The most experienced Courier of Triplet, Ravagin, will lead her to its hidden worlds--Threshold, Shamsheer, and Karyx--and introduce her to their secrets, including their advanced technology, their dark magic, and the captivating demon culture of the innermost planet. But though they begin their journey with only scholarly research in mind, Danae and Ravagin quickly find themselves embroiled in the menacing dynamics roiling throughout Triplet. Will Ravagin be able to get them both out alive?