This was getting into speculative territory, so Liza sat upright and tried to strike an authoritative pose. “Well, technically only one of them would be a serial killer, because the other would have only killed one person. But I more mean—” What did she mean? “I more mean that three people have said that this Mr B character is real, and that either he’s here or his agent is here. And if he is—or she is; after all, Mr B is a pseudonym—”

Hanna raised a sardonic eyebrow. “Lean in, girl boss.”

“Hey, women can be mass-murdering crime lords too. It’s the twenty-first century.”

That made Hanna laugh. “You’re right. Carry on.”

“Anyway, if we assume that Mx B is here, then things get—well, they’re still a bit weird, but once you factor in an actual professional criminal, some things make more sense. Like I can’t imagine cracking the safe of a middle-aged hotel manager is that tough for a legend of the underworld.”

“So, how does this get us to two killers?”

In theory, it was nice to get a follow-up question, because it showed Hanna was genuinely involved, not just nodding and smiling politely. In practice, it made Liza second-guess herself. A week ago, assuming they hadn’t just got out of a massive row, she’d have been overjoyed if Hanna had made an interesting observation about the murder of Laetitia Toureaux or the crimes of Elizabeth Báthory. Now it felt much more urgent and much more on-the-spot-putting. It was great to be seen, but being seen was just two steps away from being seen through. “Well, it’s not the only way it could have worked,” Liza tried. “Maybe Sir Richard is right and we’ve got a ‘Ten Green Bottles’ scenario. But I can’t shake the feeling that if anybody was going to push Malcom Ackroyd off a balcony, it was probably his wife.”

Hanna nodded, either in agreement or encouragement.

“But I don’t think Vivien Ackroyd could have stolen the gun and killed Belloc. Then again, if somebody in the hotel was secretly a criminal mastermind who Belloc was pursuing, having him suddenly swerve off after another killer and get shot by them would be a really convenient way to get rid of him.”

“And after that you’d need to tie up the loose end?”

“Exactly.” Liza shrugged. “Or, y’know, not. Maybe I’m just making things up so that it all fits into a nice little box.”

Having exhausted the analytical potential of scraps of paper on carpet, they tidied up, neither really wanting to leave a rug full of paranoia for the cleaners to find when they came in to turn the bed down.