“He told us they’d been together for ten years,” said Beauvoir. “That meant they met in 2005. What else happened that year?”

“Guillaume Couture died,” said Lacoste. “Antoinette moved into his home, and the obit appeared in the McGill Alumni News. Brian Fitzpatrick was an alumnus. He admits now he recognized Gerald Bull in the photo.”

“But how did he even know about Gerald Bull?” asked Cohen. “He’s not a physicist.”

“No, but he was an opportunist,” said Lacoste. “He’d become fascinated by the story of Dr. Bull. In the interrogation tonight, Brian admitted he found out about Gerald Bull and Project Babylon while researching the area for a surveying course. Baby Babylon was mentioned in some obscure publications, and on digging deeper he found vague references to another possible missile launcher Bull had planned. Bigger, more powerful.”

“Worth a shit-load of money,” said Beauvoir.

“What started as a lark, a kind of hobby to find out more about Gerald Bull and this secret testing ground, turned into an obsession,” said Lacoste.

“And when he saw the obit,” said Beauvoir, “and realized Dr. Couture must’ve not only worked with Bull, but been close enough to have been with him in Brussels, that’s when Brian decided to come down and make the acquaintance of Couture’s only living relative.”

“Antoinette,” said Cohen. “Ten years ago.”

“He’s told us everything now,” said Lacoste. “With the plans gone and the gun found there’s nothing left for him.”

“But how did you know it was Brian Fitzpatrick who’d killed Laurent and Antoinette?” asked Cohen.

“It was, finally, very simple,” said Isabelle Lacoste. “As I went back over the file, over the statements and evidence, and the sequence of events, a few things became clear. The killer had to have been in the bistro that day when Laurent came in. He had to have heard the story of the gun and believed it. That narrowed the suspects down considerably. It also had to be someone who didn’t know the boy well. Who left the stick behind. And it had to have been someone who knew that Antoinette would be alone that night. Who fit? A few people.”

“But only one person knew that Brian would be away in Montréal all night,” said Beauvoir. “And that was Brian. He was also in the bistro when Laurent came roaring in.”

“Most of what we knew about Antoinette, and especially the night of her death, we heard from Brian,” said Lacoste. “And most of it was a lie. Including that she was expecting guests. But what he didn’t know was that she’d begged off of Clara’s party and was taking her uncle’s things to the theater instead. To get them as far away from her as possible.”

“And that was another clue,” said Beauvoir. “The fact Antoinette did it when Brian was away instead of asking for his help.”