Mirkwood is indeed murky – it's dark, stuffy, and feels claustrophobic.
Eventually, they reach a river.
Everyone crosses the river in groups on a little rowboat.
But, unfortunately, a stag comes bounding into the dwarves and knocks Bombur (the heaviest dwarf) into the river.
They rescue Bombur from the water, but he's not safe just yet.
He keeps falling asleep and having strange dreams about a feast.
The other dwarves have to carry Bombur's heavy butt through the forest, and they aren't too happy about it.
They also keep hearing odd giggling in the woods: "The laughter was the laughter of fair voices not of goblins, and the singing was beautiful, but it sounded eerie and strange, and they were not comforted" (8.30).
They've run out of food, they are thirsty, and Bombur keeps waking up just long enough to talk about his dream feasts.
One night, they see lights through the forest, and they decide to go off the path (against the direct instructions of Gandalf and Beorn).
They stumble onto an elvish feast.
Thorin approaches the elves.
Suddenly, the lights go out.
Bilbo hears the dwarves calling each other's names in the dark, but they're growing more and more distant.
He's lost alone in the dark. So he does what any hobbit would do: he falls asleep.
But Bilbo wakes up just in time to find a spider wrapping him in thread.
He pulls his knife and stabs at the spider until it dies. Close one!
He slips on his ring and creeps invisibly through the forest.
Eventually, he hears the hissing of spiders speaking to each other: they've got the dwarves wrapped up in their webs!
Bilbo starts throwing stones and singing jeering songs at the spiders: "Here I am, naughty little fly; / you are fat and lazy. / You cannot trap me, though you try, / in your cobwebs crazy" (8.97).
The spiders are so angry that they chase Bilbo's invisible voice away from the dwarves.
Then Bilbo sneaks back to free the dwarves.
The dwarves do their best to fight off the spiders when they come back to the clearing, but they aren't very strong after being hung upside down and poisoned.
So Bilbo has to use his ring to lure the spiders a second time.
When Bilbo and the dwarves meet up again, Bilbo tells them all about his ring of invisibility.
They're now very impressed by Bilbo's quick-thinking and good luck.
But just then, they notice that they are one dwarf down: Thorin is gone!
When Thorin walked up to the elves' feast, the elves took him captive for interrupting their feasting.
Thorin refuses to explain to the king of the Wood-elves what has brought his people to Mirkwood.