Tobias discovers that Elfangor is his biological father in this episode. In the books, this was found out in #23, The Pretender.
When Tobias sees the boy spray-painting the hawk, he only finishes the main hawk image and not the small images on the outside. Tobias makes an imprint of this main image. When he scans it into the computer however, the smaller images are present on the physical imprint, but the disappear again when the image is presented on the screen.