In the last film of the original 91 film series two letters - one written in spite and another in love - end up in the wrong hands, while 91 and 87 as usual try to avoid ending up in military arrest.
| Actor | Role |
|---|---|
 Stig Grybe91 Karlsson | 91 Karlsson |
 Holger Höglund87 Axelsson | 87 Axelsson |
 Gun JönssonElvira | Elvira |
 Fritiof BillquistRevär | Revär |
 Gösta BernhardNot listed | Not listed |
 John NorrmanNot listed | Not listed |
 Siv EricksNot listed | Not listed |
 Åke GrönbergNot listed | Not listed |
 Lissi AlandhNot listed | Not listed |
 Stig JohansonNot listed | Not listed |
 Gunnar 'Knas' LindkvistNot listed | Not listed |
| AArne SöderbergNot listed | Not listed |
 Gösta KrantzNot listed | Not listed |
 John MelinNot listed | Not listed |
| NNils "Knas" OhlsonNot listed | Not listed |
| LLasse PetterssonNot listed | Not listed |