A Keen Betrayal is the story of Meandre, a hybrid teenager, serving humans in the Monroe Collective, one of the last human enclaves standing, after the war. She is a Keener, hybrids with special anatomy that allows them to run on all fours, making them faster and less visible to their violent enemies. Her job is to patrol the outlands, looking for impending Shadowbeast attacks.

Responding to a call for help leads her to Dustin, a boy who had been tasked with testing a new machine intended to deter hostiles. Instead of knocking them out, it disintegrates a small Shadowbeast, sending the others to their knees, wailing. Shocked, because this isn't an emotion they're supposed to possess, Dustin is consumed by guilt and wonders how much of what they've been told about Shadowbeasts is a lie - and whether he should pursue this hidden truth by seeking out his enemy's home and finding out for himself.

Meandre, meanwhile, finds herself drawn to Dustin, even though centuries of years ago, their DNA was stripped of the ability to feel romantic love. She is pleasantly confused and when Dustin asks her to accompany him to look for the Shadowbeasts base, she must decide whether to go and be close to him or stay behind and put her duty first.

This is a sci-fi YA novel that delves into the questions of love, duty, guilt, and evolution. Meandre, accompanied by Dustin, is thrust on an exciting, twisting adventure of shocking revelations, leaving them both wondering who the real monsters are.