Ghurghutiar Ghotona(1999)

An old man from Ghurghutia village near Palashi invited Feluda to solve a puzzle. The man's pet parrot recites a numeric code which is actually the combination number of his iron chest. The parrot says— Trinayan, o trinayan, ektu jiron. When Feluda solved the puzzle, he gave him four rare books of Émile Gaboriau as a reward. The very next day when Feluda returns to Kolkata with Topshe, something fishy smells in the old man's house. He started the last time investigation and it revealed that it was all a made-up plan and there was a murder behind the entire plot.