Episode 1x01, Pilot Part 1

Charlie helps Sayid build a bonfire to signal rescuers.
He invites himself to go with Jack and Kate to find the transceiver in the front of the plane. Charlie is pleased to tell Kate that she must recognize him from his band, DriveShaft. He is the bassist. When they find the plane, Charlie disappears. He is found in the bathroom, searching for something. Charlie, Jack, and Kate flee the plane when some unseen force chases them.

Charlie falls and Jack goes back for him. Charlie finds Kate, but not Jack and when they double back to find Jack, they find the mutilated body of the pilot high up in a tree.

Episode 1x2, Pilot Part 2

Kate asks Charlie what he had been doing in the cockpit bathroom and he lies and says he was throwing up.

Episode 1x3, Tabula Rasa

Charlie begins to form a bond with Claire as they collect luggage.

Episode 1x6, House of the Rising Sun

Charlie sneaks into the jungle for a heroin fix and steps on a beehive. As the bees chase them, Kate finds two corpses in the caves. Charlie again sneaks away for a hit and Locke finds him and demands the drugs. Charlie reluctantly gives up the drugs and Locke points out Charlie's guitar on a cliff.

Episode 1x7, The Moth

Charlie asks Locke for his drugs a second time and Locke gives him a moth metaphor.
Charlie crawls through a hole to save Jack from a cave in. He asks Locke for his drugs a third time, and Locke gives them to him. Charlie burns the drugs.

Episode 1x8, Confidence Man

Charlie makes a deal with Claire that if he can find her some peanut butter she will move to the caves.

Unsuccessful, he gives her a pretend jar and she agrees to move.

Episode 1x10, Raised by Another

Charlie believes that Claire is in danger and wants to protect her.

Episode 1x11, All the Best Cowboys Have Daddy Issues

Charlie is with Claire in the jungle when she goes into labor. Once the contractions pass and they believe it was a false alarm, they head back to the caves, but are stopped by Ethan.
Charlie is found by Kate and Jack hanging by his neck from a tree and Jack is barely able to bring him back to life.

Episode 1x14, Special

Charlie doesn't know what happened with Ethan in the jungle. He is in shock and upset that they only wanted Claire. He does his best not to read Claire's diary, but finally gives in and tells Jack and Sayid about her reoccurring dream of a black rock.

Episode 1x15, Homecoming

Ethan tells Charlie to bring Claire or one survivor will die each day until he does. When Jack's posse captures Ethan, Charlie comes out of hiding and shoots and kills Ethan against Jack's wishes.

Episode 1x16, Outlaws

Charlie is acting strange until Sayid tells him it's okay to feel bad about killing Ethan.

Episode 1x21, The Greater Good

Charlie wants Claire to rest and takes care of her baby. The only way he can keep the baby from crying is by making Sawyer talk.

Episode 1x24, Exodus Part 2

Charlie wants a gun to protect Claire and her baby from "the Others". Sayid refuses to give him one and when Claire's baby is stolen, Charlie blames Sayid. Charlie and Sayid go after Rousseau to get Claire's baby back. Not knowing Charlie's past, Sayid tells him the small plane has heroin in it as they pass the plane. Charlie gets hurt in the jungle, but refuses to go back without the baby and asks Sayid to make his head stop bleeding so that he can go on. Charlie is extremely upset with Rousseau for taking the baby and calls her a nut job and pathetic.