Dr. Henry Jekyll is a complicated character, though readers don't get a full picture of him until he explains his deeds and choices in the final chapter. Like all humans Henry Jekyll is, as he puts it, a "composite." His nature is both good and evil, civilized and primitive. Intrigued by this dual nature and wanting to experience the two separately, Jekyll finds a way to indulge his darker passions without it becoming known. Jekyll applies his knowledge of chemistry and invents a "tincture" that separates his good from his evil identity and even creates an entirely different body for each self. (Edward Hyde is his evil persona.) Above all Jekyll is almost classically arrogant. He believes he can reconstruct his own identity in order to break humanity's shared ethical rules and England's social norms, and without paying a price. Obviously he is wrong, and this novella is an account of his errors and how he pays for them.
Two related examples of imagery in Mark Twain's "Cub Pilot on the Mississippi" are his initial vivid description of Captain Brown and later description of their fight. Another example is his explanation of his criticism of Brown’s speech.
