It looks like I did not define this well enough. The psychic can employ this secret against any number of people. However the effect is only temporary, lasting until the mental signature of that person changes. Normally this takes a few days (I.e. d6 or so days) but could be faster if the said person was subjected to intense emotion or trauma or longer if they live a placid life.
Face requires you to see the person in question and they must have REAS 1 or more for it to work.
You can combine it with brain lock.