A man is chosen by his world's creator to undertake a momentous mission before an apocalyptic flood cleanses the world.

Tubal-cain: I have men at my back, and you stand alone and defy me?
Noah: I'm not alone.
Ila: This is the end of everything.
Noah: The beginning. The beginning of everything.
Noah: A great flood is coming. The waters of the heavens will meet the waters of earth. We build a vessel to survive the storm. We build an ark.
[Noah wakes up from a vision]
Naameh: Did He speak to you?
Noah: I think so.
Naameh: Will He help us?
Noah: He's going to destroy the Earth.
Noah: You know why I've come?
Methuselah: Yes. Before he walked on, my father Enoch told me that one day, if man continued his ways, The Creator would annihilate this world.
Noah: So what I saw is true? All life blotted out because what man has done? Can it not be averted?
Methuselah: Noah, you must trust that He speaks in a way that you can understand. So you tell me. Can this destruction be averted?
Noah: No.
Methuselah: Oh.
Noah: He sent me here. Why send me if there's nothing I can do to stop it?
Methuselah: Well, perhaps He simply sends you here to share a cup of tea with an old man.
Ila: [to Naameh, as she is in labor and terrified] Please, keep it inside. Please.
Noah: Fire consumes all. Water cleanses. It separates the foul from the pure. The wicked from the innocent. And that which sinks from that which rises. He destroys all, but only to start again.
Noah: Ham. What are you doing?
Young Ham: It's pretty.
Noah: You see those other flowers? How they're attached to the ground? That's where they should be. They have a purpose. The sprout. And they bloom. The wind takes their seeds and more flowers grow. We only collect what we can use, and what we need. Do you understand?
Og: Watchers have learned to fear men.
Young Ham: Then why are you helping us?
Og: The Creator formed us on the second day. They day He made the heavens. We watched over Adam and Eve. Saw their frailty and their love. And then we saw their fall. And we pitied them. We were not stone then, but light. It was not our place to interfere. Yet we chose to try and help mankind. and when we disobeyed The Creator, He punished us. We were encrusted by your world. Rock and mud shackled our fiery glow. Still, we taught mankind all we knew of Creation. With our help they rose from the dust, became great and mighty. But then they turned our gifts to violence. Only one man protected us. Your grandfather Methuselah. We were hunted, Most of us killed. Those who lived were left prisoners in these stony shells, marooned upon this barren land. We begged The Creator to take us home. But He was always silent. And now you claim that you have heard His call. Samyaza cannot accept this. A man? When it is men who broke the world. But I look at you and I see a glimmer of Adam again. The man I knew. The man I came to help.
Naameh: Snakes are coming, too?
Noah: Yeah. All that creeps, all that crawls, all that slithers.
[first lines]
Lamech: From Adam to Seth, Seth to Enosh, Enosh to Kenan, Kenan to Mahalalel to my father, Methuselah, then to me. Today, that birthright passes to you, Noah. My son.
Noah: We broke the world - we did this. Man did this. Everything that was beautiful, everything that was good, we shattered. Now, it begins again.
[last lines]
Noah: The Creator made Adam in His image, and placed the world in his care. That birthright was passed down to us. To my father, then to me, and to my sons, Shem, Japheth, and Ham. That birthright is now passed to you, our grandchildren.
[touching each baby]
Noah: This will be your work, and your responsibility. So I say to you, be fruitful and multiply and replenish the earth.
Ila: You don't have to go.
Ham: I don't belong here. For what it's worth, I'm glad it begins again with you. Maybe we'll learn to be kind.
Poacher Leader: What do you want?
Noah: Justice.
Noah: The time for mercy has passed. Now our punishment begins.
Noah: Some things cannot be unbroken.
Ila: Will he come back?
Noah: Some things cannot be unbroken.
Ila: I have to know. Why did you spare them?
Noah: I looked down at those two little girls and all I had in my heart was love.
Ila: Then why are you alone, Noah? Why are you separated to your family?
Noah: Because I failed him, and I failed all of you.
Ila: Did you? He chose you for a reason, Noah? He showed you the wickedness of Man and knew you would not look away. And you saw goodness too. The choice was put in your hands because he put it there. He asked you to decide if we were worth saving. And you chose mercy. You chose love. He has given us a second chance. Be a father, be a grandfather. Help us to do better this time. Help us start again.
Methuselah: I am Shem.
Noah: My oldest.
Shem: Come closer. Let me see you. You're a lucky boy. I think you must have your mother's looks, not your father's.
[winks]
Tubal-cain: The ark, the beasts, and all of your women are now mine. I will build a world in my image!
Noah: Soon everything we knew of creation will be gone. All that is left of Creation will lie within these walls. Outside, just the waters of chaos again.
Tubal-cain: When I heard talk of miracles, I dismissed them. But then I saw the birds with my own eyes, flying here, and I had to come.
Noah: There isn't anything for you here.
Tubal-cain: No? This all belongs to me. This land. This forest. That stronghold of yours. Did you really think you could protect yourself from me in that?
Noah: It's not protection from you.
Tubal-cain: Then what is it?
Noah: An ark to hold the innocent when The Creator sends his deluge to wipe out the wicked from this world.
Tubal-cain: The Creator does not care what happens in this world. Nobody has heard from Him since He marked Cain. We are alone. Orphaned children, cursed to struggle by the sweat of our brow to survive. Damned if I don't do everything it takes to do just that. Damned if I don't take what I want.
Noah: We have been entrusted with a task much greater than our own desires.
[after being mortally wounded by Tubal-cain, Samyaza looks up and sees the heavens open]
Samyaza: [weakly] My Creator... forgive me.
[Samyaza explodes and his angel form ascends back to heaven]
Og: [to the other Watchers] The Creator brings him home!
Noah: We are to see Methuselah. My grandfather.
Samyaza: A child of the old one? You should have killed them.
Og: But, Samyaza...
Samyaza: This is a man, Og. Do you forget how they betrayed The Creator?
Noah: It is He who sends us?
Samyaza: It lies. Leave them here to rot.