Part I and Part IV of this poem deal with the Lady of Shalott as she appears to the outside world, whereas Part II and Part III describe the world from the Lady's perspective. In Part I, Tennyson portrays the Lady as secluded from the rest of the world by both water and the height of her tower. We are not told how she spends her time or what she thinks about; thus we, too, like everyone in the poem, are denied access to the interiority of her world. Interestingly, the only people who know that she exists are those whose occupations are most diametrically opposite her own: the reapers who toil in physical labor rather than by sitting and crafting works of beauty.
Part II describes the Lady's experience of imprisonment from her own perspective. We learn that her alienation results from a mysterious curse: she is not allowed to look out on Camelot, so all her knowledge of the world must come from the reflections and shadows in her mirror. (It was common for weavers to use mirrors to see the progress of their tapestries from the side that would eventually be displayed to the viewer.) Tennyson notes that often she sees a funeral or a wedding, a disjunction that suggests the interchangeability, and hence the conflation, of love and death for the Lady: indeed, when she later falls in love with Lancelot, she will simultaneously bring upon her own death.
Whereas Part II makes reference to all the different types of people that the Lady sees through her mirror, including the knights who "come riding two and two" (line 61), Part III focuses on one particular knight who captures the Lady's attention: Sir Lancelot. This dazzling knight is the hero of the King Arthur stories, famous for his illicit affair with the beautiful Queen Guinevere. He is described in an array of colors: he is a "red-cross knight"; his shield "sparkled on the yellow field"; he wears a "silver bugle"; he passes through "blue unclouded weather" and the "purple night," and he has "coal-black curls." He is also adorned in a "gemmy bridle" and other bejeweled garments, which sparkle in the light. Yet in spite of the rich visual details that Tennyson provides, it is the sound and not the sight of Lancelot that causes the Lady of Shalott to transgress her set boundaries: only when she hears him sing "Tirra lirra" does she leave her web and seal her doom. The intensification of the Lady's experiences in this part of the poem is marked by the shift from the static, descriptive present tense of Parts I and II to the dynamic, active past of Parts III and IV.
In Part IV, all the lush color of the previous section gives way to "pale yellow" and "darkened" eyes, and the brilliance of the sunlight is replaced by a "low sky raining." The moment the Lady sets her art aside to look upon Lancelot, she is seized with death. The end of her artistic isolation thus leads to the end of creativity: "Out flew her web and floated wide" (line 114). She also loses her mirror, which had been her only access to the outside world: "The mirror cracked from side to side" (line 115). Her turn to the outside world thus leaves her bereft both of her art object and of the instrument of her craft--and of her very life. Yet perhaps the greatest curse of all is that although she surrenders herself to the sight of Lancelot, she dies completely unappreciated by him. The poem ends with the tragic triviality of Lancelot's response to her tremendous passion: all he has to say about her is that "she has a lovely face" (line 169). Having abandoned her artistry, the Lady of Shalott becomes herself an art object; no longer can she offer her creativity, but merely a "dead-pale" beauty (line 157).