After Professor Lidenbrock buys an old Icelandic saga, he finds a mysterious document inside it, written in code. With a magnifying glass, he is able to discern that the document was written by Arne Saknussemm, a sixteenth-century Icelandic professor and alchemist.

Lidenbrock explains to his nephew Axel that these alchemists were the learned men of their day and made important discoveries. He imagines that the mysterious document Saknussemm wrote in code would reveal important information if they could decipher it.

As they get to work on it, it is Axel who breaks the code and realizes that Saknussemm wrote in Latin but that the document must be read backwards. When Axel reads what the alchemist wrote, he decides not to tell his uncle that it is about journeying to the center of the earth. He fears his uncle would actually try to make the dangerous trip.

However, the nephew can't withhold his discovery long and informs his uncle that the mysterious message says that if they enter the crater of a certain Icelandic volcano before July, they will be able to travel to the center of the earth. The note also says that Saknussemm himself did this. As the nephew suspected, his uncle is determined to repeat Saknussemm's feat, and the two men, along with their guide, Hans, follow in Saknussemm's footsteps as they make their perilous journey.