Tobias, a figure from the Old Testament Apocrypha, was the son of Tobit. Tobit was blinded by some sparrows' droppings which fell into his eyes. He sent his son on a journey to receive some money which was owed to him. Accompanying Tobias were his guardian, the archangel Raphael, whom he thought was a mortal, and his dog. Tobias bathed in the river Tigris, where a giant fish leapt from the water. Raphael told him to catch it and when they returned home Tobias used the gall of the fish as a cure for his father's blindness.
In an earlier episode, Tobias and Raphael met Sarah, who was bewitched by a demon. Tobias married Sarah and the demon was exorcised.
Raphael revealed his true identity after Tobias cured Tobit's blindness.