Private detective Tatyana Ivanova has no easy cases. But this one… In a matter of days, without even managing a snack or getting much sleep, she darts around the city, searching for the one person who could poison well-known businesswoman Inna Rassova. But who is it? How did they get into the presentation in her luxurious mansion? And for what reasons did they go for murder? After enormous effort, Tanya figures out their name and understands: there are no motives for a crime. Then who poured cyanide into that fateful glass of champagne? In the end, Tatyana finds both the reason and the culprit—but… lets the murderer go free! And once again she follows them, tailing them…