Bilbo's leaving has ripples within the Shire far beyond a year's worth of gossip and bother.
Among other things, along with Frodo's behavior following Bilbo's leaving, there's pretty much a permanent black mark on that branch of of the Baggins family. Bilbo dismisses the expected disturbance as a matter of gossip for "a year and a day," but people talk about it so long that it morphs into the Legend of Mad Baggins, confabulating his adventures into an urban legend about a hobbit who disappears in a flash of light only to return with treasure. Outside the realm of urban legend, the general consensus is that Bilbo finally went completely off the rails, came to some sort of unfortunate end after running off, and that Gandalf is all generally to blame. Not that they are entirely wrong, Gandalf is generally to blame, and the ring did mess with Bilbo's mental state.
Frodo steps right up into Bilbo's shoes as the local eccentric rather than settling down and developing some "hobbit-sense." There's not settling down and starting a family for Frodo, rather he stays living alone and keeps an active social life, particularly among the younger (and more Tookish) hobbits. Rather than mourning Bilbo, Frodo continues on Bilbo's birthday party tradition for so long that the Shire stopped even questioning it. What really marks Frodo as eccentric is his predilection for wandering, sometimes with Merry and Pippin, who suspect that on his own Frodo visits with the elves.
In many ways Frodo's life is in a holding pattern for some 20 years. The regret of staying behind never leaves him, yet he's never quite ready to follow in Bilbo's footsteps. A certain restlessness pervades his life, as well as a curiosity about the world at large. I can't help but wonder how much of the tug-and-pull on his life is the influence of the Ring, and on that unnameless other power that Gandalf sees in Bilbo rather than an orc finding the Ring.
Regardless of the insularity of the Shire, rumors of strange, and sometimes dark, happenings at the world at large do creep in. Even rumors of ents are heard by hobbits who would avoid any news of far away lands. Elves passing westward to the sea and not returning, dwarfs on the road in unusual numbers, and other strangers briefly infringing on the boundaries of the Shire as roads wind on. Perhaps Frodo alone seeks out these travelers and the news that they carry.
Tolkien drops a lot of knowledge and foreshadowing on us in this interim. We learn about Mordor and the growing power there that was once in the Mirkwood, the elves leaving Middle-Earth, the appearance of intelligent orcs and trolls, and that there are worse creatures yet to be named. We even learn about the ents, though not by name (regardless of their mention earlier in this post), a bit of lore almost as forgotten as that of the hobbits. All of these rumors come to play significantly in the story to come, even if the initial significance is lost on a new reader.
Gandalf's final return is a signal of change, a catalyst for our story. We now know that the rumors are more than just idle chatter, the Ring is fully revealed as a major player in its own right, and exactly how close the Ring was to gaining control of Bilbo. The importance of free will is introduced as well, the willing and voluntary surrendering of power. And while not said, the importance of free will in accepting power, free will that Gollum never knew enough to properly exercise, and free will that will come in to play with Frodo later on.
The poem of the rings of power itself is one of those enduring pieces of literature, with a strong meter, though I am always left wondering when the translation from another language retains its meter and rhyme. Of interest in the following history lesson is that the rings of power distributed among the races were not of Sauron's making, that he exerted his power over them and corrupted them as they fell to his touch. The rings of the Elf-lords were held out of Sauron's reach, but even those are at risk should Sauron regain control of the Master Ring.
The history of the Ring is one of betrayal and corruption, the death of kings the cost of its emancipation from Sauron's hand. Then the betrayal of it's next bearer, slipping from Isildur's finger as he escapes from orcs. I feel that while the Ring corrupts, it does so best when the seeds already lie there. Isildur came from a line of great kings, known for their selflessness and wisdom, he had no need for greater power or wealth. Smeagol's fall to me is indicative of the sprouting of characteristics already present, a twisting of his existing curiosity and strength. That his first act is to kill for ownership of the Ring, at a time when it's power has lain largely dormant for time unknown, must give the ring a stronger measure of control over him, and his actions afterward do not serve to benefit him but contribute to the spread of strife and discord until Smeagol is driven away. As Gandalf remarks, Bilbo was rewarded for demonstrating pity and mercy rather than striking Gollum down.
That Gandalf tortures the truth of of Gollum stands out as a particularly dark detail, even when left at the vague "I put the fear of fire on him." While Gandalf makes shows of power, by and large that is not his primary method of navigation through the world, generally relying on subtly and study. Though Gandalf demonstrates his normal foreknowledge in predicting that Gollum will have some significant part to play in the fate of the Ring.
Ultimately, Frodo must resolve to leave the Shire, for himself and for the life that he knows.
"I should like to save the Shire, if I could - though there have been times when I thought the inhabitants to stupid and dull for words, and have felt that an earthquake or an invasion of dragons might be good for them. But I don't feel like that now. I feel that as long as the Shire lies behind, safe and comfortable, I shall find wandering more bearable."
There's a definite emphasis on the importance of home, of a place of sanctuary and peace. In some ways this is a very hobbitish feeling, but it's also something that transcends race and is one of the reflective ideas that Tolkien has included in his fiction.
The chapter is presented to us here out of order in the film, opening with scenes of Barad-dur, Gollum's torture by agents unknown, and riders heading out. It's extrapolation to say that Sauron's minions tortured Gollum, but considering the general demeanor of the parties, it's a reasonable assumption, and more palatable to the audiences than seeing Gandalf torturing him. Our footage of Gandalf in this is of research, sharing with us the finding of the ring of power and further history of Middle Earth.
There's a general compression of about 20 years here, cutting the story rather neatly and concisely. In having watched the full trilogy of both Lord of the Rings and The Hobbit, this neat trimming is almost shocking in retrospect. In this case I think the trimming is to the actual passage of time, not just exposition. In terms of overall story-line, this only gets squirrely when looking at the specifics of ages and dates, with some potential to effectively shrink the size distances traveled by significantly downplaying the time passed.
Once back at the Shire we're treated to a happy night out with a foreboding return to Bag-End. Gandalf here is one possessed with concern bordering on fear, a fear that is infectious. The mood of the scene is clearly communicated through tight focus and dark lighting.
We don't get the full "birth" of Gollum, here, but just enough to remind us of his connection to the Ring. We will get this done beautifully at the beginning of The Return of the King, with Andy Serkis embodying Smeagol just as well as he did as the motion-capture basis for Gollum. I like the full filming of the discovery of the ring, rather than relegating it to pure exposition. especially as Gollum becomes such a dynamic character through the films.
The discovery of Samwise is a break in the mood, with a misunderstanding on the meaning of "eavesdropping" and a plea to not be turned into anything "unnatural." We do lose Samwise's joy at the opportunity to meet elves, and instead only Sam's dread and Frodo's relief at the companionship in his journey. From here we jump immediately to Gandalf leading Frodo and Samwise on a day-time journey, instructing them to be wary of spies and to leave the name Baggins behind, before leaving them for tasks of his own. This jumps a little ahead of the book, but is consistent with the pressing urgency of the story as portrayed through the film.