While this seems an almost insurmountable task for such a voluminous novel, you will need to only consider the most important parts of the plot which really come at the end of Melville's tome. But, the metaphysical considerations, such as Ahab's search for what "lies behind the pasteboard mask" of nature as he seeks the white whale, do deserve mention, too.
Here are some major points that you can consider in summarizing Moby Dick:
- A strange, rather melancholy young seaman named Ishmael, who narrates the novel, begins his odyssey in Nantucket, Massachusetts, where he meets a South-Sea Islander and cannibal called Queequeq, who signs on the Pequod as a harpooner with Ishamel as shipmate.
- After the ship sets sail, the captain does not come on deck for several days; when he does, Captain Ahab, "a grand, ungodly, godlike man" as described by Captain Peleg, startles Ishmael with his white bone leg and ghastly white scar that runs the length of his face; during his appearance on deck, Ahab offers a sixteen-dollar-goldpiece to the first who sights the white whale, whom he says holds an "inscrutable malice." He, then, has a ritual performed much like communion in which the crew drink from a flagon and the harpooners cross their lances, pull off the ends and drink from the "long, barbed godlets."
- Despite several successful hunts, the crew do not see Moby Dick; during this time, the ship hits the duldrums and Queequeq strangely orders a coffin built for himself while Ahab rages at the world.
- Torn between the influences of his good first mate and the malevolent Fedallah, who suddenly appears on board one day to act as Ahab's demonic advisor, predicting that Ahab will know "neither hearse nor coffin," he will see two hearses on the water, one of which is "not made by human hands," and only hemp and rope can kill Ahab. The captain turns his ship around to where he first encountered Moby Dick, and eventually spot him.
- For three days, the crew pursues Moby Dick without success, but on the third day, with Ahab's harpoon stuck in him, Moby Dick turns around to the Pequod, striking it with his head and sinking it.
- The prophecies of Abdullah are fulfilled, as he gets caught in the ropes and is drowned as the ship sinks; Ahab becomes entangled in the rope also, and the whirlpool created by the sinking ship sucks down all the crew but Ishmael, who floats by holding to Quequeeq's coffin. He is saved when the Rachel, whose captain had been refused Ahab's help in finding his son, comes past and rescues him.