Unusually, although most of the tight focus is on a woman, the psychology under study is that of her son, who is a compulsive liar. It's a pretty good, and thus pretty horrifying, portrayal of his motivations and numerous failed attempts to change. The ending, just at the dawn of WWI, is a great mic drop moment. There's definitely some weird early 20th century class-based genetics ideology at work in parts of it, which some may find a little disturbing.