- Jacob is probably the "him" that Ben referred to while being held in the armory in the Swan Hatch.
- Episode 3x6, I Do
Pickett tells fellow Other, Jason, "Ben just put his life in the hands of one of them!" He draws his gun. "Shephard wasn't even on Jacob's list."
- Episode 3x16, One of Us
Ben tells Juliet that Jacob will cure her sister's cancer.
- Episode 3x20, The Man Behind the Curtain
Ben takes Locke to see Jacob. Ben talks to an empty chair and Locke thinks he's crazy, but as Locke is leaving, he hears a voice (that may not have been Jacob) saying, "Help me." The door closes, the lantern falls, the room shakes, and windows break. For a brief moment, Locke thinks he sees someone sitting in the chair.
- Episode 4x1, The Beginning of the End
Hurley finds Jacob's cabin and looks inside. It's very dark, but he sees a man in the rocking chair. The man looks like Christian Shephard. Someone looks out the window right in front of Hurley and it startles him and Hurley runs away. (May not have been Jacob.)
- Episode 5x16, The Incident
Jacob makes his own thread and works on a tapestry. Then he goes into the ocean and pulls a fish out of a trap. He fries the fish on a rock above a fire. He watches a ship out in the ocean. Another man comes over and Jacob asks if he's there for the ship. The man says yes and says that he knows how the ship found the island, that it was Jacob. He also says that he wants to kill Jacob and Jacob says he knows. The man says that someday he's going to find a loophole. Jacob is sitting under the statue.
Many years later, Jacob goes to see Kate when she is a kid. She is caught stealing a lunch box and he pays for the lunch box. He visits Sawyer on the day of Sawyer's parents' funeral and gives him a pen so that Sawyer can finish his letter to Mr. Sawyer. He brings Locke back to life after Locke falls out the window from the eighth floor. He talks to Sayid while Nadia is hit by a car, and he's waiting in a cab for Hurley when Hurley gets out of prison. He tells Hurley to get on Flight 316 and he leaves Hurley the guitar case.
On the island, Locke and Ben go into the four-toed statue. Jacob looks at Locke and says, you found the loophole. Jacob tells Ben that he has a choice and he doesn't have to do whatever Locke has told him to do. Ben is upset because he'd always done everything Jacob wanted, but Jacob never acknowledged him. He wants to know why Locke can come to see Jacob, but Ben was never allowed to. Ben says, "What about me?" and Jacob says, "What about you?" and Ben stabs him several times. The man who looks like Locke pushes Jacob into the fire.
- Episode 6x1, LA X
Jacob appears to Hurley and tells Hurley that he died an hour ago. He also tells Hurley that he's got to save Sayid and to take him to the Temple.
- Episode 6x5, Lighthouse
Jacob appears to Hurley and tells him that he and Jack need to do something. He gives Hurley a bunch of instructions, which Hurley writes on his arm. When Hurley tries to do the mission by himself, Jacob tells him that he has to bring Jack.
After Hurley and Jack find the lighthouse and Jack smashes the mirrors, Jacob tells Hurley that Jack has something to do, but he needs to figure it out for himself.
- Episode 6x9, Ab Aeterno
In 1867, Jacob attacks Richard when Richard comes to kill him. Jacob asks if a man wearing black sent him and Richard says yes. Richard says that he's dead and they're in Hell and Jacob dunks him in the ocean a few times until Richard says he wants to live.
Jacob explains to Richard that the darkness is like the wine in a bottle. It swirls around, but it can't escape. The wine is like Hell and the cork is like the island. Jacob brings people to the island, but then he gives them free will. Jacob says that everyone he has brought to the island has died and Richard says he should help them. Jacob doesn't want to, but asks Richard if he will on Jacob's behalf. Richard agrees and Jacob makes Richard stop aging.
Jacob goes to Man in Black. He says that Man in Black tried to kill him and Jacob says that Man in Black will never leave the island as long as Jacob is alive. Man in Black says he'll kill Jacob and Jacob says that someone will replace him. Man in Black says he'll kill the replacement too.
- Episode 6x15, Across the Sea
Mother helps Claudia deliver Jacob and then his brother, then she beats Claudia to death with a rock.
As a teenager, Jacob sees that his brother has a game that consists of a playing board and white and black stones. Jacob asks what it is. Teenager in Black says it's a game and you play it. Jacob asks how he knows how and Teenager in Black says he just knows. Jacob wants to know how to play and Teenager in Black says he'll show him only if he promises not tell Mother, because she'll take it away. Jacob promises.
Jacob goes back to the cave dwelling and says hello to his mother and helps her with the string she's using to weave a tapestry. She asks what he and his brother were doing and Jacob says they were walking on the beach. She asks if he loves her and he says yes. She says, "Then tell me what happened."
Later, Jacob and his brother get spears and chase after a boar. They see other men and are shocked. They run back to tell Mother and she seems worried. She says that she and her boys are there for a reason, but it's not time yet.
She blindfolds them and leads them out into the jungle. They ask if she knew about the people and she says yes. She hadn't told them because they are dangerous and she didn't want to frighten the boys. They ask what makes them so dangerous and she says, "The same thing that makes all men dangerous. They come, they fight, they destroy, they corrupt. It always ends the same."
She tells the boys that the people are from the other side of the island and to stay away from them or they will hurt the boys because they are people and that's what people do. Teenager in Black wants to know if that means they can hurt each other. Mother stops and takes off their blindfolds and says that she has made sure they can never hurt each other.
She turns them around and they see a cave with amazing light coming from it. She says that is the reason they are there, because of the light. Every man has a little bit of the light in them, but they always want more, so she's protected this place, but she can't protect it forever and one of them will have to take over.
Later, Jacob and Teenager in Black play the game, but Jacob makes a move that Teenager in Black says he can't do. Jacob asks why and Teenager in Black says, "I found it. One day, you'll find your own game and everyone else will have to follow your rules."
Teenager in Black says he's taking a walk and leaves.
That night, Teenager in Black wakes Jacob and they sneak out. He tells Jacob to follow him to the people and they argue. Teenager in Black says their mother lied and she doesn't love them, and Jacob tackles him and hits him. Mother breaks them up and Jacob says that Teenager in Black is leaving. Mother tells him that no matter what anyone tells him, he will never be able to leave the island. Teenager in Black wants Jacob to go with him, but Jacob decides to stay with Mother.
The next day, Jacob asks Mother why she loves Teenager in Black more than she loves him and she tears up and says that she loves them in different ways.
As a grown man, Jacob works on the tapestry. His mother is making something with her mortar and pestle and he asks if she's alright. She says she's just tired.
Jacob goes across the island and watches his brother's people, then plays the game with his brother. Teenager in Black asks if Mother knows that Jacob visits him and Jacob says she never asks about him.
When Jacob returns home, Mother asks what Man in Black said and Jacob says that he finally found a way off the island.
That night, Mother wakes Jacob, telling him that it's time. Jacob goes with her to the light. She asks him to drink something which will mean he accepts his responsibility to protect the light. He doesn't want to, but she convinces him. She says that going into the light would be worse than death.
After gathering firewood, Jacob goes to his dwelling, where he sees that Man in Black has killed Mother. Man in Black tries to explain, but Jacob beats him and then drags him to the light. He throws him down in the creek and Man in Black hits his head and then floats face down into the light, where he disappears.
Suddenly, the smoke monster comes rushing out above Jacob. Jacob walks away and finds Man in Black's body. He carries the body back to the dwelling where he sets it up with Mother's body. He positions them so they are holding hands and places a black and a white stone in a pouch that he puts on Man in Black. He says, "Good-bye, brother."
- Episode 6x16, What They Died For
As Hurley walks through the jungle with Jack, Sawyer, and Kate, he sees young Jacob. Jacob says he wants the ashes that are in Hurley's pocket. Hurley wants to know why, but young Jacob takes them and runs. Hurley chases after him and comes upon adult Jacob at a campfire. Jacob says, "Get your friends. We're very close to the end, Hugo."
Hurley comes back with Jack, Kate, and Sawyer. Jacob apologizes for the loss of lives. He says that one of them needs to take over as protector of the island. Kate wants to know why her name was crossed out, and Jacob says it's because she became a mother, but the job was still hers if she wanted it.
He tells them to sit and tells them that he made a mistake and created what they call the monster. The island needs to be protected from him. Jack says he'll do it. This is what he was meant to do.
Hurley, Kate, and Sawyer watch as Jacob chants over some water and then gives it to Jack to drink. Jack asks how long he'll have to do the job and Jacob says until he can't do it anymore. After Jack drinks, Jacob says he's like him.