Two weeks before the murder Mr. Renauld changes his will in which his son does not get any money. However, the culprit kills Mr. Renauld even though in order to actually get this money they would also have to kill Mme Renauld. Did they have any plans to do it or were they simply unaware of that fact?
Previously Renauld’s will had divided his fortune between his wife Eloise (under a trust) and his son Jack:
‘Ah, that reminds me of another point,’ said M. Hautet [the examining magistrate]. ‘Did Monsieur Renauld take you into his confidence at all as to the dispositions of his will?’
‘I know all about it—took it to the lawyers for him after he’d drawn it out [said Stonor, Renauld’s secretary]. I can give you the name of his solicitors if you want to see it. They’ve got it there. Quite simple. Half in trust to his wife for her lifetime, the other half to his son. A few legacies. I rather think he left me a thousand.’
‘When was this will drawn up?’
‘Oh, about a year and a half ago.”
Agatha Christie (1923). The Murder on the Links, chapter 10. Project Gutenberg.
But Renauld’s plan to fake his death and escape to another country required him to change his will, as he did not want to let Jack in on the plan, and it would be inconvenient if his money were encumbered by a trust:
‘Renauld sees only one way of escape—death [said Poirot]. He must appear to die, in reality escaping to another country where he will start again under an assumed name and where Madame Renauld, having played the widow’s part for a while, can join him. It is essential that she should have control of the money, so he alters his will.’
The new will therefore left everything to his wife unconditionally:
‘All seemed square and aboveboard [said Lucien Bex, Commissary of Police]. The only thing at all out of the ordinary was his [Renauld’s] will. Here it is.’
Poirot ran through the document.
‘So. A legacy of a thousand pounds to Mr Stonor—who is he, by the way?’
‘Monsieur Renauld’s secretary. He remained in England, but was over here once or twice for a weekend.’
‘And everything else left unconditionally to his beloved wife, Eloise. Simply drawn up, but perfectly legal. Witnessed by the two servants, Denise and Françoise. Nothing so very unusual about that.’ He handed it back.
‘Perhaps,’ began Bex, ‘you did not notice—’
‘The date?’ twinkled Poirot. ‘But, yes, I noticed it. A fortnight ago.’
Jack indicates, when questioned, that he was unaware that his father had made a new will:
‘You were aware, then [said Poirot], of the terms of your father’s will?’
‘I knew that he had left half his fortune to me [said Jack], the other half in trust for my mother, to come to me at her death.’
And since Jack did not know this, neither did Marthe Daubreuil:
‘But what possible motive could Marthe have for murdering Mr Renauld?’ I [Hastings] argued.
‘What motive! [said Poirot] Money! Renauld was a millionaire several times over, and at his death (or so she and Jack believed) half that vast fortune would pass to his son.’
Therefore Marthe had believed (wrongly) that she could become rich by killing Renauld and marrying Jack. When she discovered her error, she tried to kill Mrs Renauld too, so that Jack would inherit the estate:
‘And her [Marthe’s] object was to murder Mrs Renauld?’ [said Hastings]
‘Yes [said Poirot]. The whole fortune would then pass to her son.’
Poirot says of Marthe, “I doubt if she has ever cared a straw for Jack Renauld”, so perhaps she had intended to dispose of Jack too at a suitable later date.