Meanwhile, in faraway Media, a young woman named Sarah prays for death in despair. She has lost seven husbands to the demon of lust -- Ashmodai (a demon later frequently associated with homosexuality) who abducts and kills every man she marries on their wedding night before the marriage can be consummated. God sends the angel Raphael, disguised as a human, to heal Tobit and to free Sarah from the demon.
The main narrative is dedicated to Tobit's son, Tobiah or Tobiyah (Greek: Tobias), who is sent by his father to collect a sum of money that the latter had deposited some time previously in the far off land of Media. Raphael represents himself as Tobit's kinsman Azariah, and offers to aid and protect Tobias on his journey. Under the guidance of Raphael, Tobias makes the journey to Media, accompanied by his dog. Along the way, he is attacked by a giant fish, whose heart, liver and gall bladder are removed to make medicines.
Upon arriving in Media, Raphael tells Tobias of the beautiful Sarah, whom Tobias has the right to marry, because she is related to his tribe. He instructs the young man to burn the fish's liver and heart to drive away the demon when he attacks on the wedding night. The two are married, and the fumes of the burning organs drive the demon away to Upper Egypt, while Raphael follows him and binds him. Meanwhile, Sarah's father has been digging a grave to secretly bury Tobias (who he assumes will be dead). Surprised to find his son-in-law alive and well, he orders a double-length wedding feast and has the grave secretly filled. Since he cannot leave because of the feast, Tobias sends Raphael to recover his father's money.
After the feast, Tobias and Sarah return to Nineveh. There, Raphael tells the youth to use the fish's gall to cure his father's blindness. Raphael then reveals his true identity and returns to heaven. Tobit sings a hymn of praise. He tells his son to leave Nineveh before God destroys it according to prophecy. After the prayer, Tobit dies at an advanced age. After burying his father, Tobias returns to Media with his family.
The book is also closely related to Jewish wisdom literature; nowhere is this more clear than in Tobit's instructions to Tobias before his departure for Media in chapter 4. The value of prayer, fasting, and almsgiving is particularly praised in this instruction; the Catholic Church often uses readings from this section in its liturgy. Because of the book's praise for the purity of marriage, it is often read during Catholic weddings.
Doctrinally, the book is cited for its teaching on the intercession of angels, filial piety, and reverence for the dead.
The Sadducees' challenge to Jesus of the example of the woman that had seven husbands serially (e.g., Mark 12:20-22) may have been an allusion to this book’s story, with Tobit’s righteous son Tobias as Sarah’s ultimate husband. Note that Sarah's childlessness is allusive to that of her namesake Sarah, the wife of Abraham.
The book was probably originally written in Aramaic. It appears that Jerome's version for the Vulgate was made from an Aramaic text available to him. Four fragmentary texts in Aramaic and one in Hebrew were found at Qumran.
The surviving Greek translations are found in two versions. The shorter form, called Greek I by Robert Hanhart in his edition of the Septuagint, is found in Codex Vaticanus, Alexandrinus, Venetus, and most cursive manuscripts. The Greek II version, which is 1700 words longer, is found in Codex Sinaiticus and closely aligns with the Hebrew and Aramaic fragments found at Qumran. Apparently the Old Latin (La) manuscripts are also translated from the longer Greek II version. Most English translations since 1966 have relied on the Greek II version.