The Acts of King Arthur and His Noble Knights recap

Merlin arranges Arthur's secret birth to Uther and Igraine, his fostering by Sir Ector, and his recognition when he draws the sword from the stone. Arthur secures his kingdom and establishes a Round Table fellowship, but its ideals are repeatedly compromised. Balin's anger leads to the Dolorous Stroke and an unwitting fatal duel with his brother Balan. At Arthur's wedding to Guinevere, the first quests expose both courage and failures of mercy. Nimue learns Merlin's magic and confines him, depriving Arthur of his chief counselor. Morgan le Fay then attempts to kill Arthur through Accolon and the stolen Excalibur, but Arthur survives and Morgan escapes. Gawain, Ewain, and Marhalt undertake adventures that test loyalty and relations between knights and women. The last section celebrates Lancelot's rescues, battles, and growing renown. Because Steinbeck left the adaptation unfinished, the book stops during Lancelot's early adventures rather than reaching the fall of Camelot.

King Uther desires Igraine, the wife of the Duke of Cornwall. Merlin uses enchantment to give Uther the duke's appearance, exacting a promise that the child conceived that night will be surrendered to him. After the duke's death, Uther marries Igraine, and the infant Arthur is secretly raised by Sir Ector beside Ector's son Kay. When Uther dies, Britain lacks an accepted heir. A sword appears fixed in stone with a declaration that the person able to draw it is the rightful king. Arthur removes it while seeking a sword for Kay and repeats the feat publicly, though many nobles resist his low apparent birth. With Merlin's counsel and support from allies, Arthur defeats rival kings and begins consolidating the realm. The Lady of the Lake gives him Excalibur, while Merlin warns that its scabbard is even more valuable because it protects its wearer from loss of blood. Arthur's reign begins amid both divine signs and unresolved opposition.

A damsel arrives at Arthur's court bearing a sword that can be drawn only by a knight of exceptional quality. Balin succeeds, but refuses to return the weapon after she warns that it will bring tragedy. When the Lady of the Lake demands Balin's head, Balin kills her in Arthur's hall over an old grievance and is banished. He nevertheless serves Arthur in the campaign against King Rience and travels with his brother Balan before their paths divide. Pursuing another enemy, Balin enters King Pellam's castle and, when his own weapon breaks, seizes a sacred spear to strike Pellam. The blow devastates the surrounding land and becomes the Dolorous Stroke. Later Balin and Balan meet as unidentified opposing champions, fight with equal force, and discover only after receiving mortal wounds that they are brothers. Their deaths fulfill the warning attached to the sword and turn great prowess without knowledge or restraint into catastrophe.

Arthur marries Guinevere despite Merlin's warning that the match will bring future pain. King Leodegrance sends the Round Table as part of her dowry, and Arthur establishes a fellowship whose members are meant to bind courage to mercy and loyalty. Marvels at the wedding feast generate three quests: Gawain follows a white hart, Tor pursues a stolen hound, and Pellinore seeks a lady carried away by a knight. Their adventures expose different gaps between knightly reputation and responsible action, including Gawain's failure to control violence and Pellinore's costly neglect of a person in immediate need. The Round Table oath attempts to make these lessons permanent. Arthur then loses his most important counselor. Nimue, having learned Merlin's magic while fending off his unwanted pursuit, seals him beneath stone and leaves him alive but unable to return. Merlin foresees the trap yet cannot escape it, and Arthur's court must continue without the man who arranged its foundation.

Morgan le Fay turns her knowledge of Arthur's household and of magic into a plan to replace him. Through an enchanted voyage and a forced combat, Arthur is set against Morgan's lover Accolon. Accolon receives the true Excalibur and its protective scabbard, while Arthur is given a counterfeit and does not at first know whom he is fighting. Nimue intervenes before the deception can kill the king, enabling Arthur to recover Excalibur and defeat Accolon. Learning Morgan's role, Arthur confronts the betrayal, but she escapes and casts the scabbard into water so that it cannot be reclaimed. Another magical gift sent to court is exposed as a lethal trap. The narrative then follows Gawain, Ewain, and Marhalt as they ride with women of different ages and separate for a year of adventures. Their encounters test promises, pride, desire, and the unequal power hidden beneath formal courtesy before the knights return and report what they have learned.

Lancelot leaves Arthur's court to seek adventures and is carried while sleeping into captivity by Morgan le Fay and three other queens, who demand that he choose one of them. He refuses and is freed by a young woman in exchange for helping her father in a tournament, a promise he fulfills decisively. Continuing alone, Lancelot exchanges armor with Kay and defeats challengers who misjudge the man they believe they face. He confronts Tarquin, a powerful knight who has imprisoned many of Arthur's companions, kills him after a hard fight, and releases the captives. Other encounters combine rescue with deception and supernatural danger, repeatedly testing whether courtesy and judgment can direct Lancelot's exceptional strength. He eventually returns to the Round Table with greater fame and with his devotion to Guinevere still central. The adaptation ends here, in the middle of the Arthurian cycle; the later destruction of the fellowship is not narrated in Steinbeck's unfinished manuscript.

The final completed narrative section follows Lancelot through a sequence of adventures in which he escapes Morgan le Fay and the other queens holding him, repays the young woman who freed him by fighting for her father, and resumes his wandering. He exchanges armor with Kay, defeats knights who mistake him for an easier opponent, overcomes the brutal Tarquin, and releases Tarquin's prisoners. Further traps test his judgment as well as his strength before he returns to Arthur's fellowship with his reputation enlarged. This is not the intended conclusion of Arthur's reign: Steinbeck stopped adapting Malory long before the betrayal, collapse of the Round Table, and deaths announced by the traditional legend. The published narrative therefore ends in the expansive middle of the cycle, with Lancelot celebrated, Arthur's court still standing, Morgan still a danger, and the tensions around Guinevere unresolved. Editorial material following the story records the unfinished project's development rather than completing its plot.