In this pivotal chapter, Holden Caulfield reunites with his younger sister, Phoebe, after a period of isolation and despair. This meeting occurs after Holden has been wandering through New York City, grappling with his anxiety about adulthood and his overwhelming feelings of alienation. He is deeply troubled and emotionally fragile, reflecting on his experiences and the challenges of growing up.

The chapter begins with Holden's nervous anticipation as he plans to meet Phoebe. He expresses a longing for her innocence and authenticity, which starkly contrasts with the phoniness he perceives in the adult world. When they finally meet, Holden is filled with a mix of joy and apprehension. Phoebe, with her straightforward and honest nature, represents a beacon of hope for Holden amidst his turmoil.

As they converse, Holden is initially hesitant to reveal the full extent of his struggles, trying to maintain a facade of control. However, Phoebe's perceptiveness and unwavering affection encourage him to open up. She questions him about his plans and expresses her concern for him, demonstrating a maturity that surprises Holden. Their interaction highlights the bond they share, marked by love and understanding, which provides Holden with a sense of comfort he has been desperately seeking.

During their conversation, Phoebe challenges Holden's cynical views on life and adulthood. She expresses her desire to join him in his escape, highlighting her innocence and the deep connection they share. Holden’s protective instincts for Phoebe emerge as he tries to shield her from the harsh realities of life, underscoring his desire to be the 'catcher in the rye,' a guardian of childhood innocence.

This chapter serves as a turning point for Holden, as his reunion with Phoebe instills a moment of clarity in his chaotic emotional landscape. Through her, he begins to confront the reality of his feelings and the implications of his actions. The chapter closes with a sense of tentative hope, as Holden contemplates the significance of this relationship and the possibility of finding solace in the connections he has with those he loves. Overall, Chapter 21 encapsulates a crucial moment of reconnection that illuminates the themes of innocence, protection, and the challenges of growing up.