Two Gentlemen 'N'(Dwaj panowie 'N')

Kazmierz Dziewanowicz's hobby is very strange. He collects people who were born on the 29th of February. One day he sees that in his collection there are two men with the same name, the same birth place, the same date of birth and the same parents. In the middle of the night somebody kills him. The Intelligence Agency begins investigation.