| Chief Detective-Inspector Roderick Alleyn, CID | |
| Lady Alleyn | His mother |
| Sarah Alleyn | His débutante niece |
| Miss Violet Harris | Secretary to Lady Carrados |
| Lady Evelyn Carrados | A London hostess |
| Bridget O’Brien | Her daughter |
| Sir Herbert Carrados | Her husband |
| Lord Robert Gospell (‘Bunchy’) | A relic of Victorian days |
| Sir Daniel Davidson | A fashionable London physician |
| Agatha Troy, RA | A painter |
| Lady Mildred Potter | Lord Robert’s widowed sister |
| Donald Potter | Her son – a medical student |
| Mrs Halcut-Hackett | A social climber |
| General Halcut-Hackett | Her husband |
| Miss Rose Birnbaum | Her protégée |
| Captain Maurice Withers (‘Wits’) | A man about town |
| Colombo Dimitri | A fashionable caterer |
| Lucy, Dowager Marchioness of Lorrimer | An eccentric old lady |
| A Taxi-driver | |
| Miss Smith | A friend of Miss Harris |
| Detective-Inspector Fox, CID | |
| Percy Percival | A young man about town |
| Mr Trelawney-Caper | His friend |
| James d’Arcy Carewe | A detective-constable |
| François Dupont | Dimitri’s servant |
| Mr Cuthbert | Manager of the Matador |
| Vassily | Alleyn’s servant |
| The Reverend Walter Harris | A retired clergyman |
| Mrs Walter Harris | His wife |
| The Assistant Commissioner | |
