Mrs. McFarlane
Mrs. McFarlane is John Hector's mother, and she partly causes the whole messy case because she dumped Jonas Oldacre once upon a time. And no one dumps Jonas Oldacre, no one! Of course, he waited twenty plus years for revenge. That's how Jonas rolls apparently. You never know when he'll strike in an overly-elaborate fashion. Mrs. McFarlane is a sympathetic character and she is also a handy information tool who gives us important information about Oldacre and his motives.