In this pivotal chapter, Holden Caulfield's emotional turmoil reaches a turning point as he reunites with his younger sister, Phoebe. After having wandered aimlessly through New York City, grappling with feelings of despair and alienation, Holden seeks solace in the presence of Phoebe, who symbolizes innocence and hope in his tumultuous life.

The chapter begins with Holden's overwhelming sense of loss and confusion. His mental state has been deteriorating, and he feels increasingly disconnected from the world around him. In stark contrast to his earlier encounters, where he struggled with feelings of loneliness and disappointment, the prospect of seeing Phoebe brings a flicker of light into his darkened world.

Holden sneaks into his family’s apartment, and despite his initial apprehension about being caught, he is filled with a sense of anticipation. When Phoebe appears, their interaction is filled with warmth and genuine affection. She quickly recognizes that something is wrong with Holden, embodying the role of a protective sibling who cares deeply for him. Their dialogue is imbued with genuine concern and innocence, as Phoebe does not shy away from asking Holden difficult questions about his well-being.

One of the most touching moments occurs when Phoebe expresses her desire to join Holden in his escape from the phoniness of the adult world. She offers her savings to him, demonstrating her unwavering love and loyalty. This gesture signifies her understanding of Holden's struggles and her willingness to support him, reflecting themes of familial bonds and unconditional love. Holden’s initial instinct is to reject her offer, illustrating his protective nature towards her innocence. He cannot bear the thought of dragging her into the complexities of adult life, which he finds suffocating.

Holden's interactions with Phoebe reveal his deep-seated fears about growing up and his desire to preserve childhood innocence, a theme that resonates throughout the novel. As they talk, he is reminded of the joy and simplicity of childhood, contrasting sharply with his own troubled adolescence. The chapter encapsulates a moment of clarity for Holden, as he begins to understand the importance of connection and the profound impact that love and family can have on one’s mental state.

As the chapter progresses, Holden's protective instincts toward Phoebe emerge even more strongly. He fantasizes about being the 'catcher in the rye,' a protector of children who saves them from the harsh realities of adulthood. This metaphor becomes increasingly significant as he grapples with his feelings of helplessness and the desire to shield Phoebe from the pain he has experienced.

Ultimately, Chapter 21 serves as a critical juncture in Holden's journey. The reunion with Phoebe instills a sense of hope and reminds him of the beauty that still exists in the world, despite the phoniness he perceives. Their relationship reinforces the novel’s central themes, highlighting the importance of innocence, love, and the bonds that tie family members together amidst the chaos of growing up.