Forge tells the story of Curzon Smith, a runaway slave who enlists in the Colonial Army during the American Revolution. A sequel to Anderson’s previous book,Chains, Forge begins in earnest after Curzon has been abandoned by Isabel, a fellow slave who has freed him from captivity at the end of the previous novel. Isabel has left in search of her lost sister, Ruth – an action Curzon has tried to prevent in order to keep her safe.

Curzon comes across a skirmish on the outskirts of Valley Forge. There, he intercedes as a young boy, Ebenezer Woodruff (Eben) draws down against a redcoat. Eben kills the soldier, and invites Curzon to meet him and his uncle Caleb at camp, to be properly thanked. Curzon follows but is beset by Trumbull, a conveyancer and Curzon’s former employer, who Curzon had stolen from when Trumbull refused to pay Curzon for his work. Caleb thanks Curzon for saving his nephew and bows to him. Curzon is moved by this. He signs up for a full tour, until the end of the war.

The following chapters describe life at Valley Forge – the laborious construction of the huts, which will be the army’s shelter, the terrible cold, and the lack of food, provisions, and resources. This, however, does not deter the good spirits of Curzon and his company. Curzon and his friends band together and survive the elements.

Bigotry and intolerance are a presence in the camp. Curzon runs afoul of John Burns – a scheming, flattering bigot – who spreads stories about him in an effort to sow discord. At a party thrown by the local militia leader, Curzon is mistaken for a slave. This leads to a temporary falling out between himself and Eben, whose privilege and ignorance makes him unable to understand Curzon and his fellow black men and women’s collective plight. Eben and Burns begin stealing food from the neighboring farms, but their alliance soon dissolves when Eben realizes Burns has no intention of sharing the food with his fellow soldiers. He and Curzon cook a pumpkin together, and Eben apologizes for his callousness.

Curzon and his friends continue the construction of their shelter hut – a process that requires the chopping down of trees and hauling of lumber. One day, Caleb mistakenly cleaves his ankle with his axe. The injury claims his life in the night. Burns is made the new sergeant, and a new captain is commissioned to lead their unit. Burns and two goons attack Curzon and steal his boots. The men in his company agree to share their boots between them to spare Curzon frostbite.

A blizzard hits the already flagging camp, and brings with it members of the Continental Congress from York. Among them is Bellingham, the man who formerly owned Curzon. Bellingham seems genuinely excited to discover Curzon is alive. He invites him to Washington’s headquarters to discuss life in the camp – Curzon thinks for a moment that he’ll be able to get justice for his abuse and stolen boots. But the next day, it’s clear that Bellingham has no interest or intention in such things. He attempts to take possession of Curzon yet again, insisting that he “owns” him. Curzon flees but is captured and court-martialed. He is returned to Bellingham, and made to work for Bellingham at Moore Hall – an estate where the congressmen are lodged. There, Curzon is horrified to discover Isabel, captured as well, serving as Bellingham’s maid.

Curzon spends the last third of the novel serving in Bellingham’s house while plotting his escape. He’s overseen and spied on by Gideon – a fellow slave, but one who appears loyal to Bellingham. Gideon overhears Curzon’s intention to flee with Isabel, and tells Bellingham, who threatens to take out any punishment due to Curzon on Isabel. Bellingham has also affixed a heavy iron collar to Isabel’s neck, the key for which he wears around his own. Gideon then falls ill and is rushed back to York for treatment.

Curzon and Bellingham visit the Valley Forge camp, where Curzon is immediately recognized by Eben. He shares with Curzon his plans to help him escape. Curzon tells this to Isabel, but she refuses, telling him that she’d intended to flee with Gideon, who would help her find her sister. Curzon, distrustful of Gideon, urges her to stay with him. Gideon returns, no longer dressed in fancy clothes, but rather dressed as a field hand. He and Isabel leave in the night. Curzon is heartbroken at her departure.

Curzon awakes in the middle of the night to discover that Isabel has returned. She tells Curzon that Gideon has been a spy for the British the entire time, and that her “ghosts” had compelled her to return to him. Curzon tells her the story of how he came to have his name – that it was his father’s spelling of coração, the Portuguese word for “heart.” The two finally kiss.

Spring arrives, and the army is ready to move. Moreover, the French have declared themselves as allies to America. The war is looking up, and Moore Hall is bustling with activity. Curzon intends to flee with Isabel when the army marches out of Valley Forge – he makes a wax impression of Bellingham’s key while he bathes, and he and Isabel melt down musket balls for the iron. Isabel forges letters drawing Bellingham away from the house, and the two steal as much food and money as they can find for their trip.

Bellingham returns armed, realizing that Curzon intends to flee, but seeing that Bellingham has no gunpowder on his lips or shirt, Curzon realizes that the man’s pistol is empty. The two fight, and Isabel knocks Bellingham unconscious with a shovel. They tie Bellingham up in the stable and flee with the army.