The story begins in Boston in 1773. Johnny Tremain is a fourteen-year-old silversmith’s apprentice. He works for Mr. Lapham, an aging silversmith, and lives in his house with Mrs. Lapham, the silversmith’s daughter-in-law, and Mrs. Lapham’s four daughters. Johnny is hard-working and good-natured, so he is well-liked by almost everyone and is a leader in the household. Dove, an older apprentice, resents him for this and the two boys often fight. At the beginning of the novel, the pious Mr. Lapham urges Johnny to read a Bible verse about the dangers of pride.
Later that day, John Hancock, a wealthy merchant, comes to the smithy to order a fancy sugar basin to match his existing silverware. Johnny is impressed by the work on the existing set and is surprised to find out that Mr. Lapham made it in his youth. Because Mr. Lapham is getting old and has lost some of his skill, Johnny must help him to make the sugar basin.
That night, Johnny goes walking on the Long Wharf with Cilla and Isannah, the two youngest Lapham daughters. He tells them about his past. His mother died when he was fourteen, shortly before he was apprenticed to Mr. Lapham. She was from Maine originally, but moved to Boston so that Johnny could learn to read and pursue a profitable trade. She always told him that he was related to the Lytes, a wealthy merchant family in Boston. If he was ever desperate for money, he could go to them and ask for help, using a silver cup she had as proof of the relationship. Johnny shows the cup to Cilla.
Johnny takes his mold of the sugar basin to Paul Revere, a master silversmith, for advice. Mr. Revere gives him some tips about how to make the basin better, and offers to hire Johnny if he ever needs more employment. Johnny is in a hurry to perfect the handle before it is due to Mr. Hancock on Monday, so with the help of Mrs. Lapham, he works on it on Sunday (something he is not supposed to do because it is the Sabbath). Dove and Dusty Miller, the younger apprentice, are supposed to help Johnny. However, they are annoyed by his pompous attitude so they give him a cracked crucible to put the melted silver in. The trick was supposed to be a silly practical joke to humiliate Johnny a little, but he spills melted silver all over himself and badly burns his hand. Mrs. Lapham hires Gran’ Hopper, a midwife, to heal Johnny, but she fails to keep his hand flat so it curls in on itself and becomes useless. Johnny can never be a silversmith now.
The Laphams allow Johnny to continue living with them until he finds a new job, although they make it clear that he is a burden and they need his room for their new assistant, Mr. Tweedle––a rude man who Johnny despises. Only Cilla, to whom he was betrothed before the accident, is still kind to him. Johnny tries to look for work, but his bad attitude and his injury prevent him from getting many job offers. When he gets offers for unskilled jobs, he turns them down because he believes they are beneath him. One of these unskilled jobs is work as a delivery boy for The Boston Observer, a paper that is critical of the British colonial government and advocates for rebellion. Although Johnny does not want to be a delivery boy, he befriends a printer’s apprentice at the newspaper named Rab. When he asks for work from John Hancock, Hancock rejects Johnny because he cannot write. But once the great merchant realizes that he caused Johnny’s injury by ordering the sugar basin, he sends Johnny a heavy purse full of silver.
Johnny uses the money to buy presents for Cilla and Isannah, but when he is giving her some limes, Isannah screams at the sight of his deformed hand. Johnny is deeply hurt and runs away from home, sleeping in the cemetery that night. He decides he is desperate enough to ask for help from Merchant Lyte. Although Merchant Lyte has a bad reputation and Rab is skeptical about the plan, Johnny goes to the merchant’s house with the cup. Merchant Lyte and his daughter, Miss Lavinia Lyte, laugh at Johnny and have him arrested for stealing the cup, believing this is part of a plot to trick them out of their riches. Johnny is arrested and sent to jail, and Merchant Lyte tries to bribe the Laphams not to help him.
Although the penalty for stealing is death, Rab helps Johnny to escape this fate. He accomplishes this by convincing Josiah Quincy, a Whig lawyer, to defend Johnny for free, and by getting Cilla to the trial in time to testify that Johnny showed her the cup before Merchant Lyte says it was stolen. Isannah also appears at the trial, impressing the spectators with her testimony on Johnny’s behalf. Miss Lavinia is particularly impressed by Isannah’s adorable face and hair. Johnny is found innocent and everyone goes out to dinner to celebrate. It comes out that Rab is a member of the Sons of Liberty, a group of anti-British youths who use mob violence and intimidation to fight back against the English government. Later, Johnny tries to sell the silver cup to Merchant Lyte since he no longer has any use for it, but Merchant Lyte steals it from him.
Johnny accepts the job as a delivery boy for the Boston Observer, and Rab teaches him how to ride Goblin, the company horse. Goblin is a good horse but extremely skittish and difficult to ride. But with practice, Johnny develops a friendship with the beautiful horse and impresses everyone with his riding skills. He begins to deliver the newspapers and in doing so, learns about politics and becomes a Whig––that is, a supporter of the rebels. He learns that the newspaper’s attic hosts the meetings of the Boston Observers, a group of important rebels including Paul Revere, John Hancock, Sam Adams, and others. As he becomes absorbed in his new life, he gradually becomes distant from Cilla, although he sees her occasionally and they remain friends.
In autumn 1773, the colonists become very upset because England wants to add a tax to tea. They refuse to pay taxes without political representation. Johnny, Rab, and Uncle Lorne all participate in the build-up to the great protest against this tax, the Boston Tea Party. Johnny acts as a messenger; Rab recruits boys to help storm the tea ships in the harbor; and Uncle Lorne prints posters and pamphlets urging the people to rise up against the tax. Johnny sees Miss Lavinia around town occasionally and feels very attracted to her beauty. On the night of the Tea Party, Johnny and Rab help throw the tea off of the ships and clean up afterwards to maintain a good image for the rebels. Although the protest mostly goes well, Johnny is put off by Sam Adams’s apparent appetite for violence, and the cruelty with which some Tories are treated.
The British place Boston under martial law, but Uncle Lorne continues to publish the Observer and other Whig publications. Rab becomes obsessed with getting a good musket to fight the British. One day, he accidentally touches a musket while showing Johnny how it works and is punished with a hard butt on the head. The British medical officer who helps Rab offers Johnny work as a delivery boy, so Johnny becomes a spy, using his job to get information and pass it to the rebels. In his free time, Johnny takes care of Goblin at the stables. One day, he notices that Dove has started to work at the stables as well; he was fired by the silversmith and now works for Colonel Smith, a high-ranking British officer. Rab insists that Johnny befriend Dove because he might have useful information about impending British actions. Johnny reluctantly obeys.
A British officer named Lieutenant Stranger tries to commandeer Goblin, only to find the horse too skittish for his needs. However, he offers to give Johnny lessons on how to jump with Goblin in Boston Common. Johnny slowly bonds with the British officer, although he never forgets his Whig loyalties. One day, Johnny finds out that Cilla and Isannah have gone to work as servants for the Lytes, and Mrs. Lapham has married Mr. Tweedie. Miss Lavinia has taken Isannah under her wing; she loves the little girl for her angelic beauty. She is a bad influence on Isannah’s character; the girl runs around half-clothed in mixed company and speaks saucily to Johnny. Johnny meets Mrs. Bessie, a servant of the Lytes who is secretly a Whig, though her masters are Tories.
A few weeks after they go to spend the summer at their country house in Milton, the Lytes return to Boston after being chased by a rebel mob. Johnny goes back to Milton with Cilla to fetch the Lytes’ silver so it won’t be stolen. In the empty country house, Johnny discovers a family Bible with evidence that his mother was in fact related to the Lytes. He tears out the page with the family tree and burns it, saying it no longer matters if he is related to the Lytes or not. When they get back to Boston, Johnny and Cilla have a romantic moment and talk about what it would be like to be married.
The Boston Observers hold one last meeting and discuss a recent conflict. The British have gone to the countryside to seize rebel gunpowder. Although the Minute Men arrived too late to stop them, the Observers are impressed by the turnout. They believe that they will be successful in repelling further British advances. James Otis, an Observer who has fallen out of favor, shows up to the meeting and gives a passionate speech about how violence is undesirable but necessary so that “a man can stand up” (193). Paul Revere is put in charge of spying and getting warning to outlying towns if the British decide to advance. Johnny uses his connection to Dove to learn about an impending raid on Portsmouth. He tells Paul Revere about this which leads to Revere’s famous midnight ride to warn the rebels.
One day, Johnny is nearly flogged by an unfriendly British officer. Pumpkin, a young British enlisted man whom Johnny knows from the stables, helps him escape. In return, Johnny offers to help Pumpkin desert. Pumpkin wants to do this because he is a Whig and loves America. He would rather be a farmer than fight for the British. Johnny gives Pumpkin some farmer’s clothes and puts him in touch with a farmer who will hide him from the British. He only asks if he can have Pumpkin’s musket. Pumpkin agrees to the exchange, and Johnny gives the musket to Rab. However, several weeks later, Johnny sees Pumpkin being executed for desertion in Boston Common. Johnny is terrified by the gunshots and the muskets and is relieved that his deformed hand will prevent him from ever going into battle.
It is now April, 1775. The British are preparing for an assault on Lexington and Concord, and the political climate in Boston has become very volatile. Johnny works as a messenger for Paul Revere and his fellow Observer Dr. Warren. Rab sneaks out of Boston to go to Lexington and fight with the militia there. Johnny is worried that Rab is too eager to put himself in a dangerous situation. Dove accidentally reveals information to Johnny about when Colonel Smith plans to lead the assault. Johnny passes this information on to Paul Revere, who arranges for two lanterns to be hung in Christ’s Church––a signal to the rebels in Charlestown to prepare to fight. That night, the first shots of the American Revolution are fired at Lexington.
The British soldiers win at Lexington because they vastly outnumber the rebels, so they move on to Concord and North Bridge to seize rebel supplies. The British try to arrest Uncle Lorne for sedition, but he hides successfully in a feather bed. Johnny takes Pumpkin’s old uniform and goes to Charlestown to tell Dr. Warren the news from Boston. Before he leaves, he and Cilla share their first kiss at the Lytes’ house. Miss Lavinia is fleeing the country and taking Isannah with her to London. This upsets Johnny, but she tries to make amends with him by informing him that he really is related to the Lytes. They honestly did not know he was until Lavinia did some research after seeing Johnny’s widow’s peak. It turns out that Johnny’s mother, “Vinny” Lyte, was expelled from the family after marrying a French prisoner of war, Johnny’s father. Lavinia offers him some of the Lyte property if any of it is left after the Revolution.
Johnny goes to Charlestown and then walks to Lexington in order to find Rab. Although the British succeeded in raiding Concord, they were stopped in North Bridge by a massive group of Minute Men. When he gets to Lexington, Johnny learns that Rab was shot in the first volley of bullets. He visits the dying Rab at a tavern, where he is attended by Dr. Warren. The young men share a warm moment of friendship. Rab thanks Johnny for the musket and is only saddened that he couldn’t use it before he was wounded. He then sends Johnny on an errand so his younger friend won’t have to be present when he dies. When Johnny returns, he takes the news stoically and allows Dr. Warren to look at his deformed hand. Dr. Warren realizes that he can cut away the scar tissue and give Johnny back the use of his thumb. Although the operation will be painful, Johnny quickly agrees to it and goes for a walk while Dr. Warren readies his supplies. As he passes through the Lexington countryside, he thinks how proud he is of America and is people.