On a special event at the prison, 5 prisoners Lincon T-Bag Michael Paul and Sucre gave a chance to go for a sauna and can bring one thing with them.
Following are the things that the prisoners bring with them.
Lincon: A soda.
T-Bag: Thermos
Michael: Book named "How to kill".
Paul: A Walkman.
Sucre: Harmonica.

Since it is a Sauna, no one can see each other. After a while When steam is switched, Paul was found dead and there was blood all around.
Byomkesh Bakshi was called and he instantly knows who can be the murderer.

Do you?

T-Bag brings the dagger made of ice in the thermos so it does not melt. He killed the Paul with the dagger and then the dagger melts in time.