Book Log 2021 #2: Lost and Gone Forever by Alex Grecian
Change has come to the Scotland Yard Murder Squad in the wake of Walter Day's kidnapping, most notably the sacking of Segreant Neville Hammersmith, who has started a private detective agency whose primary case is finding Day and catching Jack the Ripper.
This book appears to wrap up the series, which is unfortunate as I liked the characters quite a bit and enjoyed seeing how the different factions in the Murder Squad interacted. But I guess there's not a lot of places you can go after you bring in Jack the Ripper as your villain.
It's a good end to the series, at least, wrapping things up without doing so too neatly.