After a chance meeting and an indiscreet conversation, childhood friends Tommy Beresford and Tuppence Cowley become involved in a convoluted intrigue led by a mysterious man known simply as Mr. Brown.
| Actor | Role |
|---|---|
 Francesca AnnisTuppence | Tuppence |
 James WarwickTommy | Tommy |
 Gavan O'HerlihyJulius P. Hersheimmer | Julius P. Hersheimmer |
 Alec McCowenSir James Peel Edgerton | Sir James Peel Edgerton |
 Honor BlackmanRita Vandemeyer | Rita Vandemeyer |
 Peter BarkworthMr. Carter | Mr. Carter |
| TToria FullerJane Finn | Jane Finn |
 John FraserKramenin | Kramenin |
 George BakerWhittington | Whittington |
 Donald HoustonBoris | Boris |
| JJoseph BradyDr. Hall | Dr. Hall |
 Wolf KahlerThe German | The German |
 Reece DinsdaleAlbert | Albert |
| PPeter LovstromHenry | Henry |
 Matthew ScurfieldConrad | Conrad |
| HHolly WatsonChild on Beach | Child on Beach |
| PPhyllida HewatWoman in Tea Shop | Woman in Tea Shop |
 James WalkerFirst Clerk | First Clerk |
| MMike EllesSecond Clerk | Second Clerk |
| GGabrielle BluntAnnie | Annie |
| NNorman HartleyFlorist | Florist |
| RRoger OstimeRitz Receptionist | Ritz Receptionist |
| NNicholas GeakeWatson | Watson |
| SSimon WatkinsMan at Astley Priors | Man at Astley Priors |
 Steve FletcherMessenger Boy | Messenger Boy |