Chapter 5 serves as a transition in time and as a way to fill the reader in on the details of the months that Orwell has skipped. This chapter also highlights the differences between Winston and Julia. Even though Winston now has an ally in Julia, he is still essentially alone in his thinking.
This chapter also serves to introduce the fact that Syme has been vaporized, enabling O'Brien to reference him in the next chapter and thus key Winston in to O'Brien's possible unorthodoxy. Syme's disappearance also serves as the basis of the relationship between Winston and O'Brien. Note that Winston predicted Syme's disappearance earlier in the novel; furthermore, this meeting between Winston and O'Brien had been foreshadowed in Chapter 1, when Winston relates the eye contact made between him and O'Brien.
Winston interprets O'Brien's offer of the dictionary as an obvious ruse; he truly believes that his assumption about O'Brien's faithlessness to the Party is correct. Winston realizes at this moment that that he will follow through with O'Brien's summons. This decision is the turning point, or climax, in the story. All the events thus far in the novel have led to this moment. When Winston makes this irrevocable decision, he is at his greatest personal development. Although he could choose to turn away from destiny, he chooses instead to embrace it. From this point forward, fate takes over, and Winston is powerless to stop what comes to pass.
