The plot focuses on a very close father-daughter relationship that has a number of uncomfortable truths brought to light by the discovery of a letter.
Interactions between the main characters are excellent thanks to the cinematography and physical performances of the actors. How much of it is down to strong direction by Kieslowski I am unsure, but there is a consistency to the father-daughter intimacy that makes you believe what you see is real.
I am not going to be pretentious and say I understand every bit of symbolism and imagery, but as a father I found it to be quite powerful and pretty disturbing in those Electra Complex moments. The cameo by a character from a previous episode is also perfectly timed.
The story resolves in quite a cinematic way considering it is a series of conversations. People cannot help what they feel, but how they act upon the feelings is what matters. From that perspective it ends on a positive note with the father doing the right thing. Saying that, I doubt they could ever get back to their previous relationship after making certain admissions to each other.