NOTE: This spoiler was sent in by Mary.

The movie begins with a man with brown curly hair running from a dinosaur when suddenly the earth cracks beneath him, and he begins to fall into the crack…which is filled with molten lava.  As he falls, he calls out to “Trevor”.  Just then, Trevor (Brendan Fraser) wakes up from a dream, only to stare at a picture of he and his brother, the curly haired man who fell into the crevice.

We quickly learn that Trevor is a professor who is trying to follow his brother’s work, but has quickly run out of money, support, and at seems time.  It seems that his brother initially invested in placing several volcanic monitors all over the world, but now only 3 are working [IMPORTANT].  His lab is being converted to a storage room, and he mocked badly by a snobby professor.  Trevor teaches a class on volcanic activity…only he has few students in the classroom, and all of them look quite bored. 

Trevor arrives home, only to notice his answering machine flashing with 4 messages.  All of them are from his sister-in-law, who states that she’s on her way with Sean (Josh Hutcherson), Trevor’s nephew and his brother’s son.  We also note that Trevor’s brother has been missing for 10 years now, and that Trevor is quite a sloppy house keeper. 

Trevor’s SIL arrives with Sean in tow, and Sean is not happy to be there. And Trevor is not happy to have him.  Trevor’s SIL gives him a box before she leaves, and Trevor opens it to find a baseball glove, something he can’t identify as well as a book “Journey To The Center Of The Earth.”  In the book, Trevor notices a series of notes that his brother has made and realizes that they all correspond to the 3 remaining volcanic monitors back at his soon to be closed lab.  Sean goes with Trevor to the lab, and Trevor starts to explain that each of the volcanic markers noted almost exactly the same volcanic activity…and just as he mentions this, the monitors all change to become EXACTLY what Trevor’s brother notes in the book.  Trevor explains that he has 3 volcanic monitors left that his brother set, and Sean attempts to correct him…because he sees 4 on the computer monitor.  The 4th monitor is located in Iceland, and Trevor believes that he could find his missing brother there.  Trevor wants Sean on a plane back to his mother, but Sean reminds him that Trevor’s brother is his father, and he comes along with Trevor to Iceland.

Once in Iceland, Trevor and Sean get lost but wind up at an old cabin, which is actually a scientific organization that they were searching for anyway.  They knock at the “organization” which is actually a rundown cabin, and a lovely blond woman (Anita Briem) named Hannah answers.  They ask for the leader of the organization, and quickly find out that the gentleman was Hannah’s father, who has been dead for 3 years.  Hannah invites Trevor and Sean inside her cabin, and they find out that Hannah’s father and Trevor’s brother both actually believed that the book, “Journey To The Center Of The Earth” was real, and they attempted to find the center of the earth themselves.  Trevor asks Hannah to help him find the way to the 4th volcanic monitor, and she agrees to be their paid guide…for $5000 dollars an hour.  They set off for the summit of a mountain, and Sean and Trevor find that Hannah is quite a capable and fit guide.  Sean calls “first dibs” on Hannah, and Trevor and Sean argue all the way to the top of the mountain over the fact that Sean is only 13 years old and cannot call first dibs on a woman, because Trevor should be given first dibs.  Sean ignores Trevor and follows after Hannah happily.

The 3 reach the summit of the mountain, find the monitor, and an electrical storm erupts around them. Trevor insists on retrieving the 4th monitor because he believes it holds data that could find his brother.  Unfortunately, the 4th monitor is also now a lightening rod, and it attracts the storm.  Trevor refuses to let it go, and as he runs to escape the storm and enter into the safety of a nearby cave, lightening strikes several times, collapsing the entrance of the cave.  This leaves Trevor, Hannah, and Sean trapped in the cave with no way out.  Hannah was indeed a prepared guide.  She had lights, flares, rope and other provisions, and they now have tools to escape the cave.  Hannah leads the group further into the cave, but Trevor takes over…and almost walks into a 20 story straight drop into a deep dark hole.  Hannah finds an alternative route, and they decide to start repelling into the hole.  In a funny scene, Trevor loses his footing, and Hannah decides to cut him from his rope, which freaks Sean and Trevor out.  Trevor falls almost an entire foot, and hits the ground.  Hannah knew they were near the bottom the whole time.

The 3 travelers wound up in a cave which had obviously been a mine.  Hannah noted that the mine was actually a death trap, which killed all but one of the miners years before.  Hannah started the generator to the mine, and the 3 of them climbed on mine carts on a railroad and Hannah started them on the railroad trail.  The hope was that the railroad line would eventually lead them out.  Actually, what followed was one heck of a roller coaster ride full of hills and valleys, twists and turns, and a dead end.  Trevor’s railroad car crashed into a wall, which cracked the wall.  Sean quickly climbed in, and Trevor and Hannah followed.  The cave was amazing, full of diamonds and rubies and emeralds.  Sean got busy gathering all of the diamonds he could get his hand on.  Just then, the group heard a cracking noise.  Trevor and Hannah looked down, and realized they were standing on a very thin sheet of stone, which would crack under most any pressure.  The group almost made it back out of the cave, but Sean dropped one of the diamonds he collected, and the cave floor collapsed, with the 3 of them falling. 

And falling.  And when they stopped screaming, Trevor noted that they still hadn’t stopped falling yet.  So, more falling and screaming.  Finally, Trevor started coming up with theories on how they’d land.  They could land on spiked rocks, or hit a type of water slide and fall into a pool of water.  Sean and Hannah voted for the water slide scenario, and sure enough that’s just what happened.  The three of them swam to shore after falling in the water, and they all noted iridescent blue lights flying above them.  What they soon realized was that the lights were actually blue glowing birds.  And those birds lead the group out to an opening where they found a tree house of sorts.  Trevor found his brother’s writings there, and Hannah soon found the brother’s body.  In a touching scene, Trevor buries his brother beside the shore, and reads a touching journal entry to Sean that Sean’s father wrote on Sean’s 3rd birthday.  Sean and Trevor hug, and leave Hannah to reflect on the shore. 

That night,  Trevor and Hannah talk about how to get back to the earth’s surface.  Sean approaches them, and relates that even though he’s a kid, he believes he should be a part of the conversation.  So, they explain that the center of the earth’s temperature is increasing, and they have to get out of the center within the next 48 hours or they’ll die.  Trevor’s brother wrote in his journal that he believed he could use the heat from the earth’s core to force water through a shaft in the earth to propel him back to the surface. The 3 of them decide to try his theory, and craft a raft with a sail to float across the other side of the sea in the center of the earth.

Once the group is on the sea, they become bombarded with huge piranha, and use sticks to bat the fish away.  Just as they succeed, huge carnivorous water creatures begin to eat the huge piranha fish, and they use the sail to steer away from the activity.  But the sail begins to tear away from the raft, and Sean is carried away after he attempts to grab the sail.  Hannah and Trevor reach the shore, and Hannah heads to the shaft to away the push of hot steamy water while Trevor searches for Sean.  Meanwhile, Sean has made a friend of one of the blue glowing birds, and the bird takes Sean to water, and leads him to a route which will take him to Trevor and the shaft.  Sean almost reaches where Trevor is looking for him, but meets up with the dinosaur that more than likely killed his father.  Sean runs and gets to a cave with a small entrance, but the T-Rex breaks through and is about to eat Sean, when Trevor breaks through on the other side of the cave and drags Sean out.  They run, but the dinosaur is too fast.  So, Trevor leads the dinosaur to that thin type of stone which breaks easily, and the dinosaur falls to his death.  Trevor and Sean make it to the river, which will soon steam up and take them to the surface, and Hannah meets them with a boat.  The boat is the jawbone of a dead T-Rex.  They reach the shaft, but there’s no water!  Suddenly, Trevor sees magnesium veins in the stone, and lights a flare and throws it at the vein…igniting the shaft, forcing water into the shaft and propelling the group to the surface.  The jawbone boat is shot up high into the air above the earth’s surface, and they go on yet another ride down a huge mountain…destroying a vineyard and home in the process.  The owner of the home and vineyard goes nuts, shouts at them in Italian, and they realize that they’re in Italy!  Sean pulls out a huge diamond [that he kept in his backpack the whole time] and the man asks in English, “You want to ride the mountain again?” and the group all hugs, kisses and laughs.  Trevor realizes that Sean has several pounds of diamonds in his possession, and they’re very wealthy now.

Sometime later…

Trevor walks back into his old lab at the university, with the snobbish professor there once again mocking him.  Trevor relates that he’s okay with losing his lab…as he’s buying an entire research building because he’s suddenly come into money.  And Trevor also relates to the snobby professor that he can read all about his new research in the latest Scientific magazine.

Hannah and Trevor are now together, and Sean and Trevor are quite close now.  In fact, Sean is going to come back to visit Trevor and Hannah for Christmas.  When Sean prepares to leave with his mother, he stops to feed something hiding in his backpack.  It’s the same blue glowing bird that befriended Sean in the center of the earth.