1882. London is at its murkiest yet most vibrant, wealthiest yet most poverty-stricken. No sooner does March Middleton arrive to live with her guardian, Sidney Grice, than a case presents itself: a young woman has been brutally murdered, and her husband is the only suspect. The victim's mother is convinced of her son-in-law's innocence, and March is so touched by her pleas she offers to cover Sidney's fee herself.