So to prevent any confusion: purifiers can identify other purifiers and Guardians can identify other guardians. Sometimes one Other can recognize another Guardian or Other, but it's rare. I think I've explained Others somewhere else in this thread, but to put it all here:
Others are the vessel for a Guardian's human heart. They ARE the heart, in essence, and without the Other guardians lose their humanity and become ultra-powerful, but they lack compassion or the capacity for morals. Only an Other can kill a Guardian in a way that frees them from the cycle of death/rebirth and the Guardian and their Other sometimes have a semi-psychic bond that comes and goes, mostly in the form of one knowing when the other is hurt. And of course there's the whole "destined to be together thing". Others and their Guardians are made from the same matrix of life and while Guardians are almost entirely composed of magic in a body of flesh, their Others are often far more human and may even lack the ability to access the magic that makes them up (like Dante).
Also, in the morning they're going to find Trevean's wanted posters replaced with poor sketches of a wolf-like thing.