Tashkent professor Nikolai Ivanovich Hod-kin, being near death, sketched a will for his students and employees on a notebook page. For those who remain to live, the scientist instructed to unravel the secret of the terrible disease "kala-azar," which ruined thousands of lives in Uzbekistan. Professor Khodukin managed to escape from the clutches of death. He returned to his laboratory and opened the carrier of "kala-azar...."