At first, Mr. Truaxe seemed improved upon Ms. Kilner’s return. He was in the Toronto office infrequently, which helped Ms. Kilner and the rest of the team to get things done.

But it became clear that he would not return to being the person he had been. At one point, in late summer, he and Ms. Kilner spent hours together in a New York restaurant talking about new products, one of the most normal exchanges she had with him in months. She texted her husband, telling him that she wanted to cry with happiness. Ten minutes later, Mr. Truaxe got up and said he had to leave the restaurant “because people were in there watching him.”

In August, Mr. Truaxe and Ms. Kilner cut off Deciem’s relationship with Beautylish. Mr. Johnson said that in the meeting, Mr. Truaxe seemed to be “having one of his episodic experiences” and that he talked at length about subjects that were unrelated to the business. (Mr. Johnson has not forgiven Ms. Kilner. He sees her as having enabled Mr. Truaxe’s darker tendencies; it was she who sent the email terminating the relationship.)

In an email sent on Oct. 1, Mr. Truaxe addressed the distrust for him that had grown rampant at his company. He wrote, referring to himself by his own initials and in the third person, that “I recognize that many of you may have allowed doubt to cloud your judgment of B.T., despite much kindness, love, respect and generosity that our founder has shown us.”

Eight days later, he announced on Instagram that the company would stop all operations and close down its own stores, provoking pandemonium within the company and a run on its merchandise from a consumer base worried that their preferred products would soon be unavailable. Three days later, Estée Lauder Companies successfully sued to have Mr. Truaxe removed from Deciem . Ms. Kilner, then seven months pregnant, replaced him as chief executive.