Well, you're going away from Jane Austen which means probably not late 18th-C to early 19th-C. I do think Victorian would be great fun and you could bring in Jack the Ripper (there was a novel "Black by Gaslight", which had our heroines chasing Jack the Ripper. Still not sure if it was written to be serious or not-the Victorian idioms were very funny. She had lots of "smelling-salt" scenes and "heaving bosoms" (if not actually mentioned, then clearly implied!)).