
Chiriakhana (which means Zoo in Bengali/Hindi) begins with Byomkesh and his friend cum trusted associate Ajit awaiting for their next case when it finally knocks their door. The client, Mr.Sen who is a retired judge, runs a reformist colony (named Chiriakhana) which houses some of the ex-convicts who were sentenced by him. He seeks Byomkesh's services to investigate a song that he overhears someone humming in the colony. Byomkesh figures it out to be a song from an abandoned film whose actress cum singer is accused of a murder and has been absconding ever since. One day Mr.Sen suspects something and requests Byomkesh to visit his colony urgently when someone murders him while he is still on the call. Byomkesh now has to investigate his client's murder and also link the mystery of the song with the murder.