Freely available from here, here, and other places besides. One of the better expositors can be found here:
But finally, hearing some Flatlander spout nonsense about the two-dimensionality of the universe, A Square can contain himself no longer and proceeds to espouse the gospel of higher dimensions. For this he is imprisoned for life, because the leaders of Flatland do their best to suppress knowledge of any world outside their own.
manwithoutqualities 