Holmes engages an old foe to protect his father after he learns Morland is in danger of being killed. Also, Holmes and Watson search for a killer connected to the tobacco industry when a lawyer who was in the process of reviewing a major cigarette distributor's finances is murdered.

Holmes and Watson investigate the poisoning of a relocation expert and discover the man led a decades-long secret career as a contract killer before his death. Also, Watson's path to adopting a child suffers a setback as she prepares for a home visit from her agency case worker.