alt Hacker NewsA great science fiction premise could be that a technologically advanced adversary genetically engineers mirror life people to work as spies and saboteurs at wiping out the rest of the population so they can have the world for themselves, but they get rumbled by dogs specially trained to sniff them out or various other means that might surprise and delight the reader. I vaguely remember reading somewhere that the difference between the smell of an orange and a lemon is down to the chirality of a single molecule.
Can’t tell if you’re being sarcastic or not but what you’re describing is Terminator. Early models were detectable by dogs because of rubber skin but newer models were cyborgs and had actual human skin and so were not as easily detectable and could hide among the people.