There was a lot about this that Liza still wasn’t buying. “You think she responded to workplace harassment by becoming a serial killer?”

“Don’t be silly.” Sir Richard looked borderline insulted. “I think she was already a serial killer, and Mr Ackroyd made the mistake of harassing the wrong person.”

By Liza’s side, Hanna lifted her head blearily. “Is there a right person to harass?”

“Well, somebody who isn’t a serial killer is probably a good first filter,” Ruby pointed out. “But go on, Richard, run us down the other murders.”

Sir Richard steadied himself and rubbed the sleep from his eyes with his free hand. “Well, most straightforwardly, she was staff, so she had access to the gun room—in fact, she was the one who reported the weapon missing, suggesting she even had access to the safe itself.” He took a brief pause for breath and implied applause. “She could go about the hotel without being noticed—we’ve none of us been paying attention to the staff—and could easily access the master keys. Nobody would see her as a threat, which would let her get close enough to Belloc, and to Vivien, and to Aunt Tabitha to finish them off.”

On the sofa, Hanna had almost completely stirred. “And her motivation for this is …?”

“Perhaps she’s just mad?” suggested Sir Richard.

“One,”—Hanna rolled onto her back, fatigue warring with irritation—”mad isn’t a thing. If you mean she might have a specific mental illness, you’d need to say which. Two, if you do mean she has a specific mental illness, then you should know that virtually all mental illnesses—including the big famous ones like schizophrenia—make you less likely to commit crimes and more likely to be the victim of them, not the other way around. Three, so, having worked at this hotel perfectly happily, she suddenly decides to start offing guests for no reason?”

“Not no reason.” Sir Richard, it seemed, was as keen to stick to his metaphorical guns as the colonel had been to stick to his literal ones. “She had disagreements with Mr Ackroyd and my aunt. Belloc was on her trail, and Vivien Ackroyd was in her way. It all makes a certain dark sense if you can get into the mind of a killer.”

Did it? Liza had a nasty suspicion it might. And wouldn’t that make her feel—actually, what would it make her feel? Wasn’t it better if this was all the fault of one psychopath instead of … of whatever other set of ideas she’d been working on? And Sir Richard was a proper detective—a proper amateur detective at least. What were the odds that she was right and he was wrong?