After several attacks on mercantile ships by what was identified as a giant sea monster, the government of the United States sends an expedition to kill the creature. The expedition ship finds the monster and engages in a fierce battle with it, throwing Professor Pierre Aronnax, his assistant Conseil and the Canadian harpooner Ned Land overboard on top of the creature. They discover that the "monster" is in fact a large submarine, and are quickly captured by its crew and brought aboard to meet the captain of the vessel.
20,000 Leagues Under the Sea: Captain Nemo is a hidden object game adaptation of the classic 1869 novel by Jules Verne. Most of the time, the objective is to find and click on all the items listed at the bottom of the screen on locations related to the plot, like the many rooms of the submarine cluttered with assorted objects.