What role did 21st-century criminal-science technology play in helping law enforcement officials track down and apprehend the brothers accused of setting off the April, 2013 Boston Marathon bombings? This installment of the PBS "Nova" series follows the search for the suspects and details how video surveillance, GPS records, bomb chemistry analysis, and other high-tech tools of the trade led authorities to them. 60 min. Widescreen; Soundtrack: English Dolby Digital stereo; Subtitles: English (SDH).