As the others search for “Mr. Owen,” the narrator notes, “If this had been an old house, with creaking wood, and dark shadows, and heavily paneled walls, there might have been an eerie feeling. But this house was the essence of modernity. There were no dark corners—no possible sliding panels—it was flooded with electric light—everything was new and bright and shining. There was nothing hidden in this house, nothing concealed. It had no atmosphere about it. Somehow, that was the most frightening thing of all.” As the narrator notes, nothing can be hidden in this house, especially the guilt of all the guests who inhabit it. The manner of death Wargrave chooses for himself is also symbolic, and he uses it as a clue to the real identity of the murderer on the island. He arranges to shoot himself in his forehead, the first time as a trick and the second time for real. In his confession, he notes that the mark in his head is symbolic of the “brand of Cain.”

Foreshadowing occurs when an old man sitting across from Blore on the train warns, “there’s a squall ahead … Watch and pray…. The day of judgment is at hand.” A squall will hit the island, literally and figuratively, and judgment will be pronounced and acted upon.

You should know that "Ten Little Indians" is the original title of Christie's novel, but later it was changed to "And Then There Were None" (probably for political correctness.)  Anyway, here are a few significant quotations:

"Constance Culmington, he reflected to himself, was exactly the sort of woman who would buy an island and surround herself with mystery! Nodding his head in gentle approval of his logic, Mr. Justice Wargrave allowed his head to nod... He slept..."

"People don't like a Coroner's Inquest, even is the Coroner did acquit me of all blame!"

Ten little Indian boys went out to dine; One choked his little self, and then there were nine. Nine Little Indian boys sat up very late; One overslept himself and then there were eight. Eight little Indian boys traveling in Devon; One said he'd stay there and then there were seven. Seven little Indian boys chopping up sticks; One chopped himself in halves then there were six. Six Indian boys playing with a hive; A bumble-bee stung one then there were five. Five Indian boys going in for law; One got in Chancery then there were four. Four Indian boys going out to sea; A red herring swallowed one then there were three. Three Indian boys walking in the zoo; A big bear hugged one then there were two. Two Indian boys sitting in the sun; One got all frizzled up then there was one. One Indian boy left all alone; He went and hanged himself and then there were none."