They can share a station, a mission, and a dangerous attraction. They cannot share food, medicine, microbes, or unprotected touch.
When a coupled systems failure traps twenty-one adults between two biologically incompatible habitats, xenobiochemist Lenora Quinn and nonhuman treaty architect Tarei Ninefold have fifty-two hours to build a temporary bridge between mirror-image biologies. Lenora hid the anomaly that might have changed the test. Tarei wrote the law that will sacrifice the trapped to protect two worlds.
Saving nineteen lives will require them to trust a chemistry neither government owns - and to decide whether a boundary can become the most intimate thing between them.