Mad Hatter's Holiday. The Fourth Sergeant Cribb Mystery

The beloved Sergeant Cribb series by Peter LoveseyIt's 1882 and Albert Moscrop, who is spending his holiday in Brighton observing human nature through a telescope, gradually moves into the circle of the Prothero family, who he has been fascinated by - especially the beautiful Zena Prothero, whose husband appears to take her for granted. But through this connection, he becomes involved in a sensational murder.
All of Brighton is horrified by the gruesome crime, and the local police seek the help of Scotland Yard's Sergeant Cribb and Constable Thackeray, who soon find themselves challenged by the strangest case of their careers, one as mystifying as it is macabre.