Before his death, the jeweler wrote a will in which he mentioned the famous Abbas Shah diamond. But when the heirs opened his personal safe, the diamond was not there. Without hesitation, they turned for help to detective Drongo, who, as everyone knows, is capable of unraveling the most mysterious case. The detective immediately established a circle of suspects and began to weed out those who had a cast-iron alibi. But suddenly his list began to decrease for a completely different reason - someone began to kill the suspects one by one...