The events of the next several weeks would later be picked over in minute detail by the police and the courts.

At a supper with Miss Perry on February 17th, Emile said that he had plans to meet with Madeleine the night of the 19th. It is not known whether the two did meet on the 19th, but late that night Emile suffered an attack of violent stomach pains. He recovered, however, by the following morning.

On Saturday the 21st, Madeleine went to a local apothecary and purchased a small amount of arsenic, which she said would be used to kill rats. As required by law, she signed the Poison Book at the time of this purchase.

After a night out at unknown whereabouts, Emile returned to his lodgings early the morning of February 22nd, suffering from a more severe attack than the previous one, this one leaving him bedridden for eight days.

On March 6th, Madeleine again went to the apothecary and bought more arsenic.

On March 9th, Emile had tea with Miss Perry and he said, as Perry would later testify, that "I cannot think why I was so unwell after getting that coffee and chocolate from her." Perry understood the her to mean Madeleine. Emile then told Perry that he was so in love with Madeleine that "if she were to poison me, I would forgive her." Perry chided him for even thinking such a thing, and asked what possible reason Madeleine would have for such action. "I don't know that," Emile replied. "Perhaps she might not be sorry to be rid of me."

On March 17th, Madeleine and her family returned from a trip, and the following day Madeleine made a third purchase of arsenic.

On the 19th, Emile traveled to Bridge of Allan, about five miles north of Stirling, for a week-long excursion. He returned unexpectedly on March 22nd, telling his landlady that he had received a letter calling him back, but he would return to Bridge of Allan the following day. He asked for the key to the front door, as he expected to be out late, but did not specify his destination or plans for the evening.

After midnight, early in the morning of the 23rd, his landlady awoke to a violent commotion at the front door, and found Emile outside and doubled up in pain. She helped him to his bed and called for the doctor. Emile asked for Miss Perry, and the landlady sent someone to fetch her. By the time Perry arrived, however, Emile had died.

The letter that had "called him back" was found in Emile's vest pocket, and was from Madeleine. This letter, combined with stacks of Madeleine's correspondence in Emile's room and in his desk at his office, led to the arrest of Madeleine on March 31.