The Tristram section of Le Morte d'Arthur takes up nearly a third of the total work and seems from a modern point of view an enormous digression: Arthur's knights figure in the Tristram story, but centrally the plot concerns not Arthur's court but that of a petty vassal to Arthur, King Mark. To the medieval reader, with his different but no less sophisticated esthetic expectations, the Tristram section would seem not a digression but a parallel, a second story juxtaposed with the first to serve as an exploration of the first story's meaning. The Tristram story rings changes on the whole Arthur story; that is, it presents every possible variation on the themes set up in the Arthur story, with the ultimate purpose of demonstrating dramatically that, whatever the particulars may be, once one has entered the trap of glory and chivalry, there is no way out.
Tristram's story in some ways recalls Arthur's: born while his father is presumed dead, Tristram is nearly slain by servants who would like to rule the barony themselves; he is aided by Merlin and raised by foster parents; one of his first accomplishments is to overthrow a claim for tribute; and as Arthur kills a giant who has murdered the wife of his cousin, Tristram kills a giant who has murdered his cousin.
In other respects Tristram's story parallels that of Launcelot (part of whose story has not yet appeared in Malory's legend): both run mad from love-despair; each loves the queen of his respective lord; both are trapped in bed by knights jealous of their personal glory; both are driven out of court when their adultery is proved; both plead (in identical phrases) for pardon because of their long service to the state; each triggers civil war but later becomes crucial to his lord's defense of his kingdom against enemies: Tristram, pardoned by Mark, saves Cornwall, while Launcelot, not pardoned until too late, cannot move his forces to England in time to save it.
