A husband-and-wife detective team look into the murder of one of her friends, whose father--a prominent scientist--has been kidnapped. They find themselves up against a sinister crime organization headed by a mysterious figure known only as "Z".
| Actor | Role |
|---|---|
 John BentleyPaul Temple | Paul Temple |
 Dinah SheridanSteve Temple | Steve Temple |
 Jack LiveseySir Graham Forbes | Sir Graham Forbes |
 Beatrice VarleyMrs. Weston | Mrs. Weston |
 Barbara CouperMrs. Morgan | Mrs. Morgan |
| JJenny MathotJacqueline Giraud | Jacqueline Giraud |
| AAndrew LeighProfessor Hardwick | Professor Hardwick |
| HHugh DempsterOliver Ffollett | Oliver Ffollett |
 Dino GalvaniVan Draper | Van Draper |
 Ivan SamsonMajor Murray | Major Murray |
 Bruce SetonBill Bryant | Bill Bryant |
| LLeo de PokornyDr. Steiner | Dr. Steiner |
 Michael BrennanHammond | Hammond |
 Joseph O'ConorInspector Crane | Inspector Crane |
| SShaym BahadurRikki | Rikki |
| GGerald RexErnie | Ernie |
| BBen WilliamsMr. Weston | Mr. Weston |
| AAnne HayesCelia Hardwick | Celia Hardwick |
 Peter ButterworthPost Office Engineer | Post Office Engineer |
| HHamilton KeeneAn Interested Visitor | An Interested Visitor |
| FFrederick MorantDoctor | Doctor |
| JJean PackerNurse | Nurse |
| DDennis Val Norton1st Gangster | 1st Gangster |
| MMichael Hogarth2nd Gangster | 2nd Gangster |