'Strained Mercy' opens with a more introspective Boone as he adjusts to married life with Deborah, while carrying the office by himself. Marianne works from home to care for infant Caden, recently out of NICU. Things for her go from bad to worse as developments threaten her marriage.

Aside from a voicemail from a climate scientist Sarah Richardson, worried about threatening phone calls from a climate change cult, his principal concern is Abe Freed, his journalist friend. Abe is investigating MS-13 and the Albany drug trade, and Boone worries for Abe's safety.

At the same time, Abe seeks advice from Boone about helping Chantelle, a high-end prostitute, escape a vicious pimp. Boone decides to consult Tom McAvoy and Clive Townsend for assistance. Both cases involving Freed come together in unexpected ways, with tragic results.

When the climate scientist disappears without a trace, Boone and Albany police detective Mark Wallace are frustrated by the lack of any clues as to who has taken Richardson, or her whereabouts. The case leads to an explosive resolution, presenting ethical challenges for Detective Wallace.