The original story was rather weak. 1 > It was never clear from the novel why Nishanath was interested about Sunayana. Ray at least tried to explain why Nishanath suspected the existence of Sunayan n the colony. 2 > The end of the novel was too dramatic, not much practical.
One more thing, at initial investigation Byomkesh was a bit rough with the inmates of colony, might be he was emotionally involved as he could not save client's life. Pythons, skeletons, etc. are shown to make the film more cinematic.
Strength of the movie: - 1 > Performance of Uttam Kumar, characterization was excellent. 2 > Performance of all the actors. 3 > Logical deductions and psychological analysis thru photo gallery. 4 > The theme seemed to be much practical with respect to the original story.
Weakness: - 1 > the progress of the movie was slow initially and suddenly gears up. the pace was not uniform.Ending was rather abrupt. 2 > Although Uttam Kumar tried his best, the idea of having a Japanese horticulturist. It was a bit comedy there, but overall Byomkesh was very serious throughout the movie. These two do not match. 3 > When Byomkesh was arriving in Mohanpur, it was initially a local train( no separate engine), but in the next shot it was shown that a separate engine is there. Anyhow, as this stays just for a second on the screen, the error does not have much impact 4 > When Byomkesh throws the key inside the taxi, he was too close to Dr. das. Byomkesh could have been easily noticed by Dr.Das.
Overall it was very enjoyable.