As I expected, hyoscine was the poison. That fits in with Hassendean’s journal entry and with the hypothesis I made before. Hassendean, like most people at the Croft-Thornton, had access to the hyoscine in the store. The overdose which he used gave me some trouble at first, but I think that’s cleared up. All the available evidence shows that Hassendean was a careless and inaccurate worker. From his notebook, I found that he used the abbreviation gr. for “gram,” whereas Markfield uses gm. It seems probable that Hassendean looked up the normal dose of hyoscine in a book of reference, found it given in apothecaries’ weights as “⅟₁₀₀ gr.,” and copied this down as it stood, without making a note to remind him that here gr. meant “grain” and not “gram.” When he came to weigh out the dose he meant to give to Mrs. Silverdale, he would read “⅟₁₀₀ gr.” as the hundredth part of a gram, since in laboratory work the metric system is always used and chemists never think in terms of grains. Thus Hassendean, weighing out what in his carelessness he supposed to be a normal dose, would take 0.01 grams of hyoscine. (The reference books state that serious poisoning has been caused by as little as 0.0002 gram of hyoscine). As there are fifteen grains in a gram, his quantity would be fifteen times the normal dose, which fits fairly well with the amount found in the body. He had no reason for killing Mrs. Silverdale, provided that the hyoscine obliterated her memory of that evening’s proceedings; and it seems most improbable that he deliberately planned to cause her death.
Miss Hailsham obviously does not wish to see Hassendean’s murderer caught; and therefore her identification with “Justice” is more than problematical. She may or may not have an alibi for the time of the bungalow affair, since she admits going to a dance in her car and coming away almost immediately. One may keep her case in reserve for the present.
Markfield’s car, GX.9074, is alleged to have been in an accident that night. The man who complained about it might provide a clue to Markfield’s movements, if we can lay hands on him.
The man who appeared at Fountain Street Police Station, fishing for a reward in connection with the bungalow affair, can hardly be anyone but one of the two watchers at the windows. Unfortunately, unless he chooses to talk, we have no power to extract information from him. Flamborough states that he can lay hands on him at any moment, as he is well known to our men.