Quick recap
Washington, D.C., 2019. Cross and Sampson watch the execution of a killer they helped convict. That same day, they're called to a copycat scene, with a note signed M accusing Cross of a terrible mistake. The case takes him out of D.C. to a string of scenes that mirror decades-old crimes and stir up Cross family secrets. Everything suggests the killer wants to take something Cross loves so much that losing it would wreck him. The ending wasn't checked against a reliable source, so it stays out.

