The 2013 Boston Marathon bombing kicks off a four-day manhunt, and this film reconstructs it hour by hour. It follows investigators as they comb through thousands of hours of surveillance footage and spectator photos to identify Tamerlan and Dzhokhar Tsarnaev, the brothers behind the attack, then tracks the chaos that follows: an MIT police officer shot dead, a carjacking, and a nighttime firefight in Watertown that leaves one bomber dead. The film pairs interviews and archival news footage with a plain, chronological account of how digital tools, crowd-sourced images, cell phone data, traffic cameras, worked alongside standard police legwork, door-to-door canvassing, informant tips, to close in on a suspect hiding in a backyard boat. It treats the case as a study in method as much as tragedy, showing where technology gave investigators an edge and where it didn't, and ends with the citywide lockdown that preceded Dzhokhar Tsarnaev's capture.