For millions of marathon runners worldwide, Patriots Day looms steadily and prominently on the horizon; such is the pivotal day when untold numbers journey to Boston, Massachusetts to participate in the legendary, 26.2 mile Boston Marathon. As produced by WGBH - Boston public television and directed by Daniel McCabe, the documentary NOVA: The Marathon Challenge cross-cuts between the lives of 13 Boston Marathon trainees as they psych themselves up for the "big run" during the 2007 event; the program undertakes an unusual approach, however, by specifically honing in on the underdogs - participants who are less than fit (and who lead sedentary lifestyles), but who nevertheless determine to whip their bodies into top shape for the said event despite the many obstacles and challenges that stand in their way.