Laura Lyons, not Lois Lane as we originally suspected, is the mysterious "L.L." who writes a note to Sir Charles arranging to meet him at his driveway the night he dies. By writing this letter and then not showing up, Laura gives Stapleton the opportunity to release his glow-in-the-dark hell beast on Sir Charles and literally scare him to death.
So Laura Lyons has some responsibility in Sir Charles' death, even though Sir Charles is the one who has kindly given her money to set up a typing business after her husband abandoned her and her father disowned her. Why does she do this terrible thing to someone who has been kind to her? For love, of course. Wake up, people!
The motivations of both Laura and Beryl, the two major female characters in this novel, are pretty much the same: they'll protect Stapleton as long as they believe that they have his undivided affection. As soon as Holmes proves to her that Beryl is Stapleton's wife and not his sister, Laura immediately spills the beans to Holmes about the letter that Stapleton told her to send to Sir Charles. She also admits that she had suspicions of his involvement in Sir Charles' death, but "if he had kept faith with me I should always have done so with him" (13.135).
Of course, Beryl and Laura have slightly different origin stories: Beryl is a Costa Rican woman who's an accessory to Stapleton's criminal adventures in Costa Rica and then in Yorkshire before they arrive in Dartmoor.
Laura, on the other hand, is the daughter of a local Dartmoor gentleman, Mr. Frankland, who gets married without her father's permission and winds up getting abandoned by her worthless husband. Her father, being a cranky old coot, continues to punish her for her marriage and will not support her at all. It's this double abandonment by husband and father that sends Laura running into the arms of Stapleton, who manipulates her against Sir Charles. This back-story can make her seem more of a victim than Beryl.
We feel bad about Laura's terrible luck in love (though, Doctor Mortimer does say about Laura Lyons' husband that "the fault […] may not have been entirely on one side" (10.61). In other words, Laura may not be totally innocent in the breakup of her marriage).
Like Beryl's abuse at Stapleton's hands, Laura has also been used and abandoned by the men in her life. But does that treatment relieve either of them of their responsibility in helping Stapleton? What do you guys think—Holmes and Watson don't press the case any further, but should Laura Lyons and Beryl go to jail for being accessories to murder?