It's morning, and Dorothy's thirsty. She wants to find water. The Scarecrow doesn't get why, because he doesn't have to do human things like eat and sleep.
After Dorothy breakfasts, she and the Scarecrow hear someone groaning. Dorothy traces the sound to a man…made out of tin? Yes, that's definitely a man made out of tin.
Dorothy asks the tin man if he's making the sound. Yes, he says, and he's been making it for over a year.
Dorothy pities him and wants to help. The tin man tells her that he'll feel better if she'll just oil his joints, which have rusted.
After a good long oiling session the tin man sits down for a spell. He's been frozen in that position holding his axe in the air for a whole year, after all. He deserves a break.
The tin man asks the gang what their deal is, anyway. Dorothy explains they're headed to Oz to find her a way home and get the Scarecrow a brain.
The tin man wonders aloud if the wizard might give him a heart. Dorothy doesn't see why not. They agree the tin man will join the travel party.
As they walk, the tin man tells them his story. In a nutshell, he was a woodchopper who was engaged to marry a Munchkin. The Munchkin's housemate, an old woman, wasn't so keen on the idea, so she went to the Wicked Witch of the East, who enchanted his axe.
The enchantment made the Tin Woodman (who was still human at that point) chop off one of his legs. When he had it replaced with a new one by a tin man, the witch became very angry.
The enchanted axe proceeded to cut off all his limbs. One by one they were replaced with tin. Then he chopped off his head. You'd think he might have given up and tried a new career at some point, but no.
The witch struck her final blow: the man chopped himself in half. The tinsmith replaced his torso, but now he had no heart. He fell out of love with his fiancée.
Life went on until he got caught in a rainstorm one day. He'd been standing there rusted ever since.
During that year he spent frozen in place, the tin man had a lot of time to reflect on his life and losses. He began to really regret the loss of his heart.
His new plan is to join the group to go see Oz and ask for a heart.
As the tin man and the Scarecrow bicker over which is more important, the head or the heart, Dorothy worries about her dwindling food supply. How will she ever make it back to Kansas?