The reading of this tale would be rather meaningless without the previous knowledge of the historical context of its time, specially the facts involving the Cardiff Giant statue, its creators and the profitable use they made out of it.
The narrator of the tale describes his experience in a creepy dusty New York City apartment which he had recently moved in. At the very first night he was spending there, supernatural things invaded his privacy like chains clanking, heavy footsteps and his blanket pulled out while he was tucked in his bed trembling and scared to death of these strange phenomenons. Then the responsible for all that haunting showed up, it was who claimed to be the ghost of the Cardiff Giant statue, what caused a big relief on him for, in his words, "a child might know that no harm could come with that benignant countenance."".
Having acquainted with the ghost they started talking, after a while he wondered about the ghost's tired look, asked him about it and it said it was because of haunting for so many years the museum across the street with some others ghost pals and in this museum was where laid the giant statue for visitors to watch and the ghost wanted it to be buried again so it would rest, however the character-narrator of the tale informed the ghost that the statue laying in the museum next door was a counterfeit and that the genuine one was in Albany, NY. That caused a huge disappointment and a feeling of humiliation on the ghost that slowly went away with its forsaken soul.
By knowing historically that some men took advantage of the giant's image to make money over a naive middle class at the time by charging them a certain amount in order to see the statue, we can relate it to the tale and notice the critic Twain is trying to make on the exploitation that rich people have always been doing over the poor which is one of the points that the plot tries to reach.