The scene shows an incident described in the apocryphal text of the Book of Tobit, 1-14. Old blind Tobit reclines in his chair, as his son Tobias anoints his father's eyes with the fish's gall he has brought back from his travels. The archangel Raphael, who had accompanied Tobias and returned home with him, instructs him. Raphael holds the pilgrim's staff, which symbolises the healing process, restoring sight and health. Knoller renders the scene in a darkened room lit only by a narrow beam of light. This illuminated zone emphasises and enhances the colouration of the garments in the three primary colours red, blue and yellow.