When a sickly Victorian woman dies suddenly, a postmortem reveals that her body contains a fatal dose of arsenic. Suspicion falls on her husband and her companion, who are lovers. Inspector Martin of Scotland Yard solves the mystery of her death... over a cup of tea.
| Actor | Role |
|---|---|
 David FarrarGregory Black | Gregory Black |
 Geraldine FitzgeraldElizabeth Grahame | Elizabeth Grahame |
 Roland CulverInspector Martin | Inspector Martin |
 Jean CadellEllen | Ellen |
 Mary MerrallLady Southdale | Lady Southdale |
 Harcourt WilliamsDr. Septimus Prendergast | Dr. Septimus Prendergast |
 Charles HeslopVicar | Vicar |
 Ronald AdamHead-Master | Head-Master |
| SSidney MoncktonHorace (uncredited) | Horace (uncredited) |