“Why now? Your sister has been incarcerated for three decades, but the murders only started seven weeks ago. What was going on in between?”

“Shana met someone new?” Adeline spoke up slowly but didn’t sound convinced. “Or . . . this Rose Killer . . . his or her homicidal instincts have been brewing for quite some time. The killer finally reached out to Shana, and her response lit the fuse.”

“But how do the Rose Killer and Shana find each other to even begin communicating? Her only visitor is you, right? And her only new mail has been from Charlie Sgarzi, to which she never replied. That’s why he tracked you down.”

“True.”

D.D. waited a heartbeat. She was curious if Adeline would pick up on the point that she was Shana’s only visitor. A woman who shared the same twisted gene pool. A psychiatrist who’d attended four years of medical school.

When Adeline said nothing, D.D. moved on, voice still brisk, asking for information, not sharing suspicions.

“When Superintendent McKinnon was talking,” she continued, “she mentioned that Shana’s mood changed a few months ago. She grew more depressed. Do you know why?”

“No, but Shana is hardly the type to sit around and talk about her feelings. From a clinical point of view, my sister suffers from depression. The condition is ongoing. Some periods of time are simply better than others.”

“But given that she suffers from depression, something could have happened that triggered the down cycle?”

“That’s possible.”

“But you don’t know what?”

“No. Her life is very . . . contained. Though”—Adeline’s voice picked up—“the thirty-year anniversary of Donnie Johnson’s murder is approaching, combined with Charlie Sgarzi reaching out and demanding an interview . . . That certainly could’ve triggered an emotional response in Shana. Despite what you might think, her feelings regarding Donnie are very tangled. She won’t talk about him, even now, which is almost a sure sign that day still bothers her. If she was truly remorseless, she would speak of him and/or what happened that day easily and often. But she doesn’t.”

“Okay.” D.D.’s mind was still churning. Alex had raised a good point. Timeline mattered. All killers had an inciting incident. So two, three months ago, what had happened to suddenly spring the Rose Killer onto the world?

“What do you know about so-called partner killings?” D.D. asked now, given that she was speaking to a trained psychiatrist. She continued: “Such relationships are rare. There have been a handful of husband-and-wife or otherwise ‘romantically linked’ killing teams. Couple of male cousins who killed together. Either way, there’s always one partner who’s the alpha, and one who’s the submissive.”

“You think Shana and the Rose Killer are partners?” Adeline asked sharply. “She gives the commands, he performs the deed?”

“Maybe she performs the deed,” D.D. said, then waited again.