A huge sea monster has attacked and wrecked several ships from beneath the sea. Professor Arronax bravely joins a mission to hunt down the beast. He goes aboard the Nautilus, a secret submarine helmed by the mysterious Captain Nemo. At first, the mission is exciting, as Nemo takes Arronax on a voyage around the underwater world. But when things start to go wrong, Arronax finds there's no escape from the Nautilus. He is now Captain Nemo's captive--20,000 leagues under the sea!