Anda is an overweight, British 12-year-old who loves video games. One day, she meets a famous gamer named Liza who offers Anda membership in her exclusive female gaming group, Clan Fahrenheit. The members of Clan Fahrenheit work together in one particular video game to complete missions and earn gold tokens. Over time, Anda rises through the ranks of the Clan Fahrenheit to platoon leader. She befriends an American girl named Lucy, who holds a sergeant position within the clan. Lucy tells Anda about an anonymous patron who will pay them real money for completing specific missions within the game. On each of these missions, they must traverse the world of the game, find a specific cottage, and kill all of the avatars inside. Although the cottages are sometimes guarded by experienced players, the avatars inside are always performing mundane tasks, like folding laundry, and seem unable to defend themselves. Once Anda and Lucy have killed them all, they each receive their cash reward via PayPal. Anda and Lucy are very successful on these missions, and they begin to rack in the cash.

During a particularly difficult mission, Anda comes across an avatar, Raymond, who begs to speak with her through the in-game chat. Raymond tells her that the inexperienced avatars she is killing are played by young, impoverished girls in Mexico who were hired to perform mundane tasks in the game in order to acquire gold tokens. Their boss then sells the tokens on eBay to rich players around the world who want to elevate their status in the game. The girls lose their day's wages if their avatar is killed. Anda kills Raymond's avatar, then tells Lucy what he said. Lucy doesn't believe it.

Anda's parents realize that she has developed a skin condition that often precedes type-2 diabetes. Concerned about her lifestyle, they take away her computer. She is also given medications and forced to take remedial P.E. classes.

After a month without computer access, Anda secretly goes to a PC gaming center. She logs back into the game and goes on more paid missions with Lucy. They run into Raymond again, and he shows them pictures of the impoverished Mexican girls they are about to deprive of a day's wages. Lucy argues that those girls are ruining the game economy by allowing people to buy their way into a higher level. She tries to kill Raymond, but Anda stops her. This leads to an altercation, and Anda ends up killing Lucy's avatar. Raymond tells her that rival factory owners in Mexico are paying Anda and the Mexican girls. Anda logs off, fearful that she will get kicked out of Clan Fahrenheit for killing Lucy's avatar.

Back in the PC gaming center, a boy publicly insults Anda. They get into a physical altercation before Anda runs away. Once Anda gets back home, she gets a call from Liza. Anda explains what happened in the game and is surprised to learn that Liza wants to help the Mexican girls.

Anda's father notices that she's lost weight and rewards her by returning her computer to her room. When she logs back in to the game, Anda learns that she's been promoted to Sergeant. Lucy apologizes and tells her that she's been talking to Raymond a lot. Anda and Lucy return to the game's standard missions, which aren't as exciting as the ones they got paid to do. They agree to ask Raymond how they can help.

Raymond tells them that he wants to organize a strike for the girls and alert the media, but he hasn't been able to make contact with the girls in-person in Mexico, and he keeps getting killed off in the game before he can talk to them. Anda and Lucy agree to be Raymond's in-game bodyguards.