The movie is told in five parts, and it covers the first 22 chapters of the book of Genesis.
Adam and Eve are banished from the Garden of Eden. Their son Cain kills his brother Abel. Noah builds an ark and survives the flood, along with two of every animal. God destroys the Tower of Babel. Angels destroy Sodom and Gomorrah, and Lot's wife turns into a pillar of salt. Abraham does not sacrifice his son Isaac.
God creates the world in 6 days, culminating with the creation of man, named Adam. Adam is lonely, so God puts him to sleep, takes a rib, and from it creates woman, named Eve. God gives Adam and Eve full access to the Garden of Eden, but they are forbidden from eating from the Tree of Knowledge of Good and Evil. One day, Eve is tempted by a serpent, which is actually Satan, to eat an apple from that tree She does, and then feeds it to Adam. God tells Adam and Eve that they have sinned and are banished from the Garden of Eden. Now living off of the land, Adam and Eve have two children, named Cain and Abel. As adults, Cain (Richard Harris) hates Abel (Franco Nero), because he feels that his brother is favored by God. In a fit of jealously, Cain kills Abel, then asks God if he is his brother's keeper. God marks Cain and forces him to roam the earth.
Adam and Eve have another son, Seth, and through his lineage comes Noah (John Huston, who was also the narrator, the voice of God, and the movie's director). At the time of Noah, man is wicked due to sin, and God plans to send a flood to remove man from the earth. God instructs Noah and his family to build an ark and, upon completion, place two of every animal on board. As onlookers heckle them, Noah and his family build the ark to His specifications. As they finish, the animals arrive and walk on board. As the last of the animals board the ark, the rain begins. With his family safely on board, Noah closes up the ark, and the rain falls for 40 days and 40 nights, wiping everything off of the face of the earth. Once the rain ends, and the flood waters recede to where the ark is finally on dry land, Noah and his family, as well as the animals, leave the ark. God then shows a rainbow to Noah as a promise to never again destroy the earth with a flood.
The story then moves on to Noah's great-grandson, Nimrod (Stephen Boyd). Nimrod is the King, and he has authorized the construction of a huge tower, named Babel, that will reach all the way to Heaven. God is displeased, so He destroys the tower, and sets about different languages to man so they cannot understand each other. Up to that point, all of man spoke the same language. The next story tells of another of Noah's descendants, Abram (George C. Scott). He and his nephew Lot are traveling together, along with their families, when they agree to separate their flocks. Lot chooses to travel toward the cities of Sodom and Gomorrah, which are full of sin and depravity. After that happens, God speaks to Abram. He tells him that he will be the father of the nation of Israel, and he is changing his name to Abraham. God will also bless him and his wife Sarah (Ava Gardner) with a child, even though both of them are over the age of 90. Sarah doesn't believe that she will be able to give birth to a child at her age, so she directs Abraham to sleep with her handmaiden, Hagar, and they produce a son, named Ishmael.
One day, Abraham is visited by three men, and they reveal themselves to be angels (all played by Peter O'Toole). They tell him that they are traveling to Sodom and Gomorrah to destroy the cities. Abraham asks the angels to spare the cities if they can find 10 righteous men, and they agree to do so. They arrive at Sodom, and are immediately met by Lot, who takes them to his home. As the sinful townspeople demand that they "meet" the angels, they declare that the cities do not have ten righteous men and direct Lot and his family to leave Sodom and not look back when they destroy the city. They do, but when the angels begin the destruction, Lot's wife looks back and immediately turns into a pillar of salt. A distraught Lot and his family soon rejoin Abraham at his camp. Years later, Sarah does give birth to a son, named Isaac. Because Ishmael is still there, Sarah directs Abraham to banish him and his mother. He does, but he tells Hagar that Ishmael will be the father of a nation of his own, because he is a son of Abraham.
Many years later, God speaks again to Abraham, and He directs him to sacrifice his beloved son. Abraham is crushed by the directive, but he agrees to do so. As he and Isaac travel to where the sacrifice is to occur, they come across the remains of Sodom, and he tells his son the story of the cities and of the lessons learned from it's destruction. Now at the site of the altar of sacrifice, Isaac sees that nothing was brought to sacrifice, then realizes that it's going to be him. As he places Isaac on the altar, Abraham reiterates his love of his son, but just as he is about to bring his knife down to cut his son's throat, God stops him. He tells Abraham that he has been obedient and as a result, he will bless his son with numerous descendants and prosperity. He then produces a ram to sacrifice in Isaac's place. The movie ends with Abraham and Isaac walking back to their home.