In Chapter 5 of 'The Hobbit', titled 'Riddles in the Dark', Bilbo Baggins finds himself in a dire situation after falling into a dark underground cavern while trying to escape from goblins in the Misty Mountains. As he regains consciousness, he realizes that he is alone in the dark and must navigate this new and frightening environment.

While exploring the cave, Bilbo encounters a strange creature named Gollum, who lives in the depths of the cavern. Gollum is described as a thin, wiry figure with large eyes and a hunched back, who speaks to himself in a peculiar manner. Bilbo quickly learns that Gollum is not friendly, and there is an air of danger surrounding him. In an attempt to escape, Bilbo inadvertently challenges Gollum to a riddle contest, with the stakes being Bilbo's life. If Bilbo wins, Gollum must show him the way out; if he loses, Gollum will eat him.

The riddle game begins with Gollum asking the first riddle, and Bilbo, albeit nervous, manages to respond correctly. The two engage in a series of riddles, with each trying to outsmart the other. The atmosphere is tense, and the chapter builds suspense as Bilbo struggles to think of riddles while also fearing for his life. The riddles are clever and showcase Tolkien's playful use of language, with one notable example being the classic riddle: "What have I got in my pocket?" This question is not a riddle in the traditional sense, but it leads to a pivotal moment in the story.

As the contest continues, Bilbo becomes increasingly desperate. In a moment of luck, he accidentally discovers a small, golden ring on the ground. Unbeknownst to him, this ring is the One Ring, which grants invisibility to its wearer. In a stroke of serendipity, Bilbo slips the ring onto his finger just as Gollum prepares to search for him after Bilbo's incorrect answer. The ring's power allows Bilbo to become invisible, providing him a chance to escape Gollum's clutches.

The chapter culminates in a gripping escape sequence as Bilbo, now hidden from sight, navigates through the dark tunnels. He is able to follow Gollum without being detected, leading him to the exit that Gollum had promised to show him. In a moment of cleverness, Bilbo uses the ring to evade Gollum and the goblins, escaping to the surface and reuniting with the dwarves and Gandalf outside the caverns of the Misty Mountains.

Overall, 'Riddles in the Dark' is a crucial chapter in Bilbo's journey, marking his first significant encounter with the dark forces of Middle-earth and his initial step into the realm of adventure. It develops themes of cleverness and survival, while also introducing the One Ring, a central element in the larger narrative of Tolkien's works. This chapter not only highlights Bilbo's resourcefulness but also foreshadows the profound impact that the ring will have on him and the world around him.