在2012年之后的某一年的十月二十一号早晨 （书中清楚地提到了某辆车的保险杠前一张已经退色的奥巴马2012再选广告宣传贴纸），11点44分，一个在缅因州叫做Chester’s Mill的小镇，忽然被一个不知道从哪里来的可怕的隐形半渗透膜状的屏障给罩了起来，断绝了和外界的一切联系。这个突然出现的屏障导致了一系列的伤亡事件，同时困住了前陆军上尉Dale Barbara ( Barbie)，他本来因为本地的一个争执事件而正准备离开这个镇。
警齤察局长Howard Perkins (Duke) 很快的因为接触到了屏障，而使他体内的心脏起搏器爆炸而死亡。他是市政委员 James Rennie (Big Jim)在镇上的最大阻力。Big Jim 在Chester’s Mill 有很大的影响力，而且把这次的与世隔绝当作一个可以接管整个镇的机会。
Big Jim 指派了一个和他有裙带关系，但没什么能力的 Peter Randolph 来当新的警齤察局长。同时，他还开始扩编警齤察队伍，这些靠不住的人中包括了他的儿子Junior Rennie， 和他的朋友们。Junior 常常受到头疼的困扰，只是那时候他还不知道这其实是脑瘤引起的。同时脑瘤还影响了他的精神状态。他不仅在屏障出现的时候就开始殴打并勒死一个女孩，之后杀了另一个女孩。Big Jim对此情况一无所知，还在那之后让Junior加入了警齤察的队伍。
在镇上的另外一边，本地报纸的编辑 Julia Shumway, 接到了来自陆军上校James O.Cox的通讯，他要Julia告诉Barbie与他联系。当Barbie 和上校联系上后，他要求Barbie充当政府的联络员，以便可以一起努力把这个现在被称作穹顶的屏障给消除。因为Barbie以前是寻找炸齤弹工厂的探侦员 （a former Bomb Factory Hunter）, 所以陆军上校Cox给了他在镇上寻找形成穹顶能量来源的任务。上校同时还预见到了这样的突发事件会给小镇带来的政治风波。凭借总统的指派，Barbie恢复了在军队的任职，并且还被提拔成了上校。Barbie还得到了关于准许他有不受小镇权限限制的法令公文。然而这项决定却遭到了Big Jim和他的那些被误导的随扈的阻挠。
一边Big Jim在偷偷地鼓动和精心策划，利用居民们的不安和慌乱来达到他夺权的目的。而另一边，Barbie, Julia 和其他的一些镇上的居民在尝试阻止事情急剧的失去控制。在几次阻挠了Big Jim的事情之后， Barbie被栽赃诬陷了四起谋杀案，关了起来。他被控告谋杀了帮Big Jim的大型安非他命组织洗钱的牧师Lester Coggins, 原警齤察局长Duke的老婆Brenda Perkins(这两个人其实都是Big Jim杀害的)，还有两个被他儿子Junior杀害的女孩子。当Barbie在监狱的时候，镇上的一些居民追踪到了穹顶的源头在一座废弃的农场。农场里的装置强有力的指明穹顶的源头是来自于地球以外的。Big Jim对镇上居民的管制越来越苛刻，警齤察们滥用职权，这些都促使镇上的一些居民愤而起来帮助Barbie越狱，并且就在Junior谋杀Barbie的时候，救下了Barbie,杀死了Junior。
在一个“探访日”，也就是穹顶外面的人可以和穹顶内的人在边缘见面的时候，Big Jim 派遣Randolph和一只警齤察小分队从Phil Bushey (Chef) 的手中重新夺回他对安非他命工厂的控制权。Chef之前阻止Big Jim 对安非他命工厂的掩饰，以及在那儿囤积了超过400罐的丙烷的事情。Big Jim 低估了Chef自卫的能力，以及他由安非他命所引起的妄想症。Chef和现在已经被驱逐的前首席市政委员Andy Sanders (他也在Chef的引导下使用安非他命)，一起用步齤枪来防卫他们自己和安非他命工厂。随之而来的枪战造成了很多人员的伤亡，在Chef也受了致命伤之后，他引爆了放在安非他命制作厂房的塑胶炸齤弹装置。结合了丙烷和制作安非他命时所用的化学物质，这场巨大的释放毒气的爆炸几乎把整个镇变成了一个火葬场。
上千个镇上的居民很快地被烧毁殆尽的画面在国家电视台播放着，只留下了在废弃农场里的26个幸存者，一个藏在土豆窖里的农场孤儿，和躲在镇上的防辐射尘避难所里的Big Jim 和他的副官 Carter Thibodeau。 他们最终因为食物和水而开始攻击对方（而且Big Jim担心Carter在他们幸存后会变成指认他罪行的证人）。他刺死了Carter，并且肢解了他的尸体。但几个小时之后，Big Jim就被Carter的幻象引出了避难所，接触到了有毒大气后，也死了。而尽管穹顶外的军人千方百计的想要往里输入新鲜空气，在农场幸存的人们还是慢慢地被有毒气体窒息。
Barbie和Julia 来到控制装置前祈求外星观察者能够放过他们。Julia与其中的一位女性“皮革头”联系上。这位外星人没有同龄人在左右，也就免于受到来自他们的压力。Julia重复地表达了他们是一群真实的有感觉的生物，并且也只有小小的一段生命时间。在与这位年少的女外星人分享了一次Julia童年惨痛的经历之后，她启发了这位外星人的慈悲之心。穹顶慢慢的升高并且消失，有毒气体驱散，而Chester’s Mill也最终得到了解放。
At 11:44 AM on Saturday October 21 of an unspecified year after 2012 (evident by mention of a faded bumper sticker for Barack Obama's 2012 re-election campaign), the small Maine town of Chester's Mill is abruptly and gruesomely separated from the outside world by an invisible, semipermeable barrier of unknown origin. The immediate appearance of the barrier causes a number of injuries and fatalities, and traps former Army Captain Dale "Barbie" Barbara—who is trying to leave Chester's Mill because of a local dispute—inside the town.
Po1ice Chief Howard "Duke" Perkins is soon killed when his pacemaker explodes after getting too close to the barrier. This removes the last significant opposition to James "Big Jim" Rennie, used car salesman and the town's Second Selectman. Big Jim exerts significant influence within Chester's Mill, and seizes the opportunity to use the barrier as part of a power play to take over the town.
Big Jim appoints one of his cronies, the incompetent Peter Randolph, as the new Po1ice Chief. He also begins expanding the ranks of the Chester's Mill Po1ice with questionable candidates, including his son, Junior Rennie, and his friends. Junior has frequent migraines caused by an as-yet undiscovered brain tumor which has also begun affecting his mental state; unbeknownst to Big Jim, Junior was in the process of beating and strangling a girl to death when the barrier appeared, and has killed another girl by the time Rennie places him on the po1ice force.
Elsewhere in Chester's Mill, Julia Shumway, the editor of the local newspaper, is phoned by Colonel James O. Cox, who has her carry a message to Barbie to contact him. When he does, Cox requests that Barbie act as the government's liaison in an effort to bring down the Dome, as it has come to be known. Because of Barbie's talents as a former bomb factory hunter, Cox gives him the task of locating the dome's power source, which is believed to be inside the Dome. Cox is also able to foresee the small town political ramifications of such a situation. By virtue of a Presidential order, Barbie is reinstated in the U.S. military and promoted to full Colonel. Barbie is also presented with a decree granting him authority over the township. However, smalltown politics being what they are, this action is not well received by Big Jim and his misguided band of renegade po1ice officers.
As Big Jim covertly encourages and orchestrates unease and panic among the town to build up his grab for power, Barbie, Julia and a number of other townspeople attempt to stop things from spiraling out of control. After crossing Rennie's path on several occasions, Barbie is framed and arrested for four murders. He is accused of killing Reverend Lester Coggins, who laundered money for Rennie's large-scale methamрhetamine operation, and Duke's widow Brenda Perkins, who were both murdered by Big Jim, as well as the two girls Junior killed. While Barbie is in jail, other residents track the source of the Dome to an abandoned farm, and the device is strongly indicated to be extraterrestrial in origin. The restrictions issued by Rennie become more severe and the po1ice force grows more abusive, galvanizing the town and eventually leading some residents to break Barbie out of jail, killing Junior seconds before he can murder Barbie.
The semi-organized resistance flees to the abandoned farm, where multiple people touch the strange object and experience visions. They not only conclude that the device was put in place by extraterrestrial "leatherheads" (so named for their appearance), but that specifically they are juveniles who have set up the Dome as a cruel form of entertainment, a sort of ant farm used to capture sentient beings and allow their captors to view everything that happens inside.
On an organized "Visitors Day"—when people outside the Dome can meet at its edge with people within—Big Jim sends Randolph and a detachment of po1ice to take back control of his former meth operation from Phil "Chef" Bushey, who is stopping Rennie from covering up the operation as well as hoarding the more than four hundred tanks of propane stored there (Chef wants it all, explaining, "I need it to cook"). Big Jim underestimates Chef's capacity for self-defense and meth-induced paranoia; he, as well as the now-ostracized head selectman Andy Sanders (whom Chef has introduced to meth use) defend themselves and the meth lab with assault rifles. Many are killed in the ensuing gunfight and Chef, who is mortally wounded, detonates a plastic explosive device he has placed in the meth production facility. The ensuing explosion, combined with the propane and meth-making chemicals, unleashes a toxic firestorm large enough to incinerate most of the town.
More than a thousand of the town's residents are quickly incinerated on national television, leaving alive only the twenty-six survivors at the abandoned barn, an orphaned farm boy hiding in a potato cellar, and Big Jim and his informal aide-de-camp, Carter Thibodeau, in the town's fallout shelter. Big Jim and Thibodeau eventually turn on each other over the stores of food and water (and Big Jim's worry that Thibodeau may act as a witness against him if they survive); Big Jim stabs and disembowels Thibodeau, only to die several hours later when hallucinations of the dead send him fleeing into the now-toxic environment outside. The survivors at the barn begin to slowly asphyxiate, despite efforts by the Army to force clean air through the walls of the Dome.
Barbie and Julia go to the control device to beg their captors to release them. Julia is able to make contact with a single female leatherhead, no longer accompanied by her friends and thus not caught up in their peer pressure. After repeatedly expressing that they are real sentient beings with real "little lives", and by sharing a painful childhood incident with the adolescent alien, Julia convinceѕ the leatherhead to have pity on them. The Dome raises up slowly and vanishes, allowing the toxic air to dissipate and finally freeing the town of Chester's Mill.