Jealous of her vapidly "good" sister's popularity, poisonous Viktoria doses pretty Klara's tea with a slow-acting fatal substance. As the latter grows hysterically weak, the former finds success increasingly compromised by guilt, blackmail, and the pesky need to kill others lest she be exposed.
| Directing | Juraj Herz | Director |
| Art | Zbyněk Hloch | Production Design |
| Editing | Jaromír Janáček | Editor |
| Art | Jiří Rulík | Set Decoration |
| Costume & Make-Up | Irena Greifová | Costume Design |
| Camera | Jaroslav Kučera | Director of Photography |
| Costume & Make-Up | Ladislav Bacílek | Makeup & Hair |
| Costume & Make-Up | Jiřina Bissingerová | Makeup & Hair |
| Art | Rudolf Herz | Set Decoration |
| Art | Miloš Osvald | Set Decoration |
| Sound | František Černý | Sound |
| Crew | Věra Kalábová | Dramaturgy |
| Directing | Miloš Kohout | First Assistant Director |
| Costume & Make-Up | Růžena Plašilová | Makeup & Hair |
| Costume & Make-Up | Miloslava Šmídová | Costumer |
| Costume & Make-Up | M. Koubská | Costumer |
| Camera | Jiří Pospíšil | Assistant Camera |
| Crew | Bohumila Velková | Script |
| Writing | Alexander Grin | Novel |
| Writing | Juraj Herz | Screenplay |
| Writing | Vladimír Bor | Screenplay |
| Art | Ivan Rybín | Assistant Production Design |
| Editing | Ladislava Klusáčková | Assistant Editor |
| Editing | Anna Mejtská | Assistant Editor |
| Sound | Luboš Fišer | Original Music Composer |
| Production | Ladislav Hanuš | Production Manager |
| Production | Jiří Ulrich | Unit Production Manager |
| Production | Radomír Hubáček | Unit Production Manager |
| Camera | Corina Schlesingerová | Clapper Loader |
| Camera | Karel Ješátko | Still Photographer |
| Sound | František Belfín | Conductor |
| Writing | Miloš Brož | Creative Producer |
| Production | Jiří Šebor | Executive Producer |
