The story is told in a frame format Twain meets a stranger while touring Warwick Castle, England, who presents him with a manuscript of his memoirs. The stranger is Hank Morgan, a Connecticut factory superintendent and self declared "Yankee of the Yankees" who fights with one of his men, Hercules, and is knocked out when he is hit in the headwith a crowbar. He awakes to find himself in a bucolic landscape being charged by a knight in armor. Hank is taken prisoner by Sir Kay, the seneschal of Arthur's court and brought to Camelot. Thinking that he has landed in an asylum , Hank goes along with his captor, determined to escape or "run the show." He enters Arthur's court and meets a garrulous Paige named Clarence who immediately befriendshim and tells him that it is the year 528. Hank decides to test if this statement is true by waiting for a solar eclipse that is supposed to occur on the 21st of June, two days away. When he is presented as Kay's prisoner, he is described as a horrible ogre and sentenced to die.
Hank concocts the lie that he is a great and terrible magician, and will blot out the sun if he is not released. WhenClarence reports his lie to the King, they decide to execute him a day earlier than they had planned. When Hank is taken to the stake he thinks that it is only the twentieth and that his bluff has backfired. But when the sun begins to blacken under the shadow of the eclipse, he jumps on the opportunity and majestically claims that he is responsible for the calamity. The crowd and court panic,agreeing to make Hank the king's executor in exchange for the sun.
Hank immediately uses his new position of power to institute modern conveniences and structures that he was accustomed to in Connecticut and to bring 19th c. civilization to 6th c. England. He sets up clandestine schools, factories and works hidden from the eyes of the Church, which he fears above everything else. Hank also underminesMerlin's influence on the people by exploding his tower and relegating him to obscurity. Hank takes on the title, The Boss, signifying his role as person who will run the country and direct it into modernity.
As Hank reviews a tournament, he mutters an insult at the court clown that is heard by another of Arthur's knights. Sir Sagramore challenges Hank to armed combat to occur after he has questedfor the Holy Grail for about four years. During this time, Hank carefully incubates his civilization. Towards the end of the period, Arthur sends the Yankee on a quest of adventures to gain merit and honor before meeting Sir Sagramore in combat. To do this, Hank is assigned a damsel named Alisande (whom he calls Sandy) to help her rescue some forty maidens from a castle ruled by ogres. Having nochoice but to ride with her, he dons armor and sets off from Camelot.
The task of wearing the armor proves to be almost impossible as he spends hot days and cold nights encased in the heavy hardware. He needs to be lifted onto his horse and despairs at not having pockets.
The pair encounter adventures of a comic sort, such as vanquishing challenger knights with the smoke from Hanks pipe, tomeeting up with Hank's "missionary knights" who peddle soap, stove polish and toothbrushes around the country.
Along the way, they also see many pitiable episodes of abuse and injustice, and Hank sets a dungeon full of prisoners free when he encounters them in Morgan Le Fay's castle. Finally Hank and Sandy reach the object of their task‹the ogre's castle. It is no more than a pigsty, and its captiveshogs.
After 'liberating the castle,' Hank sets off for the Valley of Holiness to restore a fountain that has suddenly stopped flowing. He telephones Camelot and tells Clarence (his now trusty sidekick) to send him chemicals and supplies to perform the "miracle." Hank knows that Merlin is already in the Valley making a magical attempt to restore the waters, and Hank plays up the opportunity to...