I don’t know that we can say there are acceptable reasons for a serial killer to commit murder, exactly, but there are certainly reasons more common than others. Even Holmes himself follows a pattern: he meets someone, discovers they have money, and murders them to get it. Sometimes he murders someone to keep them from telling other people that he murders people. But, in this case …
Lizzie (no last name given) was apparently under Holmes’ employ in the Castle restaurant. He doesn’t say exactly when this was, since most of his confessions don’t include a year. What he does say is that his janitor, Quinlan, was paying far too much attention to Lizzie, and Holmes just couldn’t have that. Apparently Quinlan was far too valuable to Holmes to get distracted because … he might reveal that his employer was a serial killer? Holmes doesn’t actually say.
Quinlan completed suicide in 1914 and left a note saying simply “I couldn’t sleep.” His surviving relatives said that he’d been haunted by the ghosts of Holmes’ victims in the months prior to his death. Because Holmes had killed so many under his nose and he hadn’t known about it? Or because he had? Quinlan was never officially accused of participating in any of Holmes’ crimes and by this point I think we all know better than to take Holmes’ word.
Instead of firing Lizzie, Holmes decided to kill her. Apparently he was worried she’d simply find other work nearby and continue to entrance his janitor. It’s that crass and that simple: he no longer wanted to employ her, so he decided to murder her.
Holmes says Lizzie was the first victim to suffocate in the by-then-infamous vault in his Castle office. He doesn’t explain how he lured her inside or how long it took her to die. Perhaps suffocation in a sealed vault was supposed to be interpreted as a peaceful death.
In a technique that he claims to use again and again, Holmes made Lizzie write letters before she died, explaining her sudden absence to her loved ones. Did he get her to hand over the letters and then shove her back inside to seal her up and wait for her to die? Or did she calmly allow herself to be suffocated without thinking that she could tear them up and ruin his plans? Clearly readers aren’t supposed to concern themselves with such grisly scemantics.
Holmes even attempts to end this description of murder on a lighter note. The prosecutor in the Pitezel case apparently offered to track Lizzie down, based on the letters she had sent, believing she was still alive. Somehow proving that Lizzie had actually gone west as her letters claimed was meant to help Holmes defend himself in the case of Benjamin Pitezel’s death by proving that he was not, in fact, a murderer. Holmes seems both amused at the notion and pleased that his ruse worked so well … although again we’re not supposed to wonder how his innocence in one case is supposed to prove his innocence in another.
Is this a serious confession so that Holmes can go to his execution with a clear conscience or a criminal gleefully crowing over his crimes?