I don't know what happened to this series but th  massive character regression for both the MC and the LI is really beyond the pale.
I have no idea what this author was thinking but out of 5 books this is the second one where it feels like Lady Emily and Colin are taken over by completely different characters. The side characters fall incredibly flat. The mystery is okay. 
I appreciate the showing how women could struggle with their prescribed roles and dealing with grief and loss when those around you expect you to move past it. That's probably the only part of this story I appreciated.