For the third year, the expedition has been searching for the causative agent of an infectious disease rampant in the Ussuri taiga, where a major construction project is about to begin. Meanwhile, the enemy seeks to destroy the fruits of years of labor of Soviet microbiologists. Young scientist Vasily Zheludev exposes a master saboteur and forces him to flee into the taiga.
| Actor | Role |
|---|---|
 Vladimir DruzhnikovNot listed | Not listed |
 Anatoliy KuznetsovNot listed | Not listed |
 Mikhail TroyanovskyNot listed | Not listed |
 Ivan VoronovNot listed | Not listed |
 Nikifor KolofidinNot listed | Not listed |
 Roza MakagonovaNot listed | Not listed |
 Liliya YudinaNot listed | Not listed |
 Nikolai BogolyubovNot listed | Not listed |
 Vladimir YemelyanovNot listed | Not listed |
 Margarita NazarovaNot listed | Not listed |
 Aleksei Alekseyevmilitia captain, arrested Mayboroda | militia captain, arrested Mayboroda |
 Vladimir VsevolodovNikita Pomazov, biologist | Nikita Pomazov, biologist |