Peter manages to get one of the
women who works for him into a post as legal clerk in Urquhart’s office. He discovers that Philip had an elderly
great aunt, a former actress who was very rich. And that she’s living in the
country, a helpless invalid. He sends
Miss Climpson, his chief detective, to her home town to try and find a way of
getting into her house.
In spite of the serious nature of the case, the book has a lot of comic
bits and Miss Climpson’s befriending of the old lady’s nurse is very
amusing. She finds out that the woman
believes in Spiritualism and uses this to find the woman’s will.
The snag is that it seems that Norman shared Philip's last meal..
and ate the same food….
Peter gets Joan Murcheson to get into Mr Urquahart's office at night, and she finds a packet of white powder which when tested proves to be arsenic. Peter works out that Urquhart has lost most of Mrs Wrayburn's money through his unwise speculations, and if Mrs Wrayburn dies, and she is very old and ill, he will have to account to Philip, who has inherited most of the money, for what he has done when acting as Mrs Wrayburn's trustee. So he makes up his mind he has to kill Philip.
Peter takes some time to think and read up on arsenic poisoning, to work out how it was done. Bunter has been going out with Hannah Westlock, Urquaharts maid, and learns that the meal was shared between the 2 cousins and that it was hedged about with precautions. Everything that was eaten was eaten by both of them. He learns however that its possible to build up a tolerance to aresnic by eating a little every day, and works out that Urquhart must have done this and so was able to eat an omelette which had been made with poisoned eggs and it caused Philip's death, but his cousin was all right. Peter puts forward this theory to Urquhart and startles him into a confession.. He tries to escape but Parker is in the flat and stops him... and charges are brought against him. Harriet is exonerated completely, but she finds that Peter, as soon as the verdict was given, has left the court and driven away. He does not want to pester her into marrying him by reminding her that he has saved her life.