John and Aoife are both able to sense psychic signatures around people, attached to their bodies and also to their belongings. The signatures are visible to them as a subtle glow of different colours. They can always see these signatures, but cannot ever show them to others. When they focus, the colours can also form a blurred image of the person. This means that they can use the ability to find and identify people's possessions, and to identify people hidden using various disguises and shapeshifting abilities. They can also locate a person anywhere in the world once they have met that individual.