"The Dog" is insanely, endlessly watchable, a compelling human-interest documentary and a riveting true-crime exploration all in one. In telling the unusual story of John Wojtowicz, whom Al Pacino portrayed in 1975's Academy Award-winning Sidney Lumet drama "Dog Day Afternoon," filmmakers Allison Berg and Frank Keraudren spent ten-plus years self-financing a rapturous real-life narrative stranger and more unpredictable than fiction. Wojtowicz is, of course, best known for the attempted August 22, 1972 robbery of Brooklyn's Chase Manhattan Bank, a crime that quickly turned into a 14-hour hostage situation ending in his arrest and accomplice Sal Naturale's death. His alleged motive—to get the money needed for his "wife's" sex-change operation—brought an additional sensationalistic element to the table, one that "Dog Day Afternoon" was ahead of its time in matter-of-factly confronting. There is much more to Wojtowicz than what happened on that steaming hot late-summer day in '72, and "The Dog" delves into his past and the decades following the failed robbery as a means of humanizing the actual man behind the myth.

As a film subject and a personality (Berg and Keraudren interviewed him from 2002 until his death, at age sixty, in 2006), John Wojtowicz is a colorful, unusual, amusingly ribald contradiction. He is a serial bisexual polygamist, described as a liar, a madman, and an occasional abuser by his first two wives, Carmen Bifulco and Ernest Aron (later Liz Eden), yet there was a smooth-talking side to him that people clearly couldn't resist. "There's sex and there's love," he says in one of his many riveting interviews. "I'm a lover." And yet, he also admits that his sole lifelong vice was of the carnal persuasion, an addiction that busted down gender lines following his first homosexual encounter with a fellow soldier during the Vietnam War. A diehard-Republican-turned-McCarthy-era-peacenik, John returned to NYC and joined the Gay Activists Alliance, holding onto wife Carmen and his two young children while engaging in a tumultuous love affair with Ernest Aron, a tortured man without the means of having the sex-change operation for which he so desperately yearned. John was against his wishes at first, but then came around—a decision that, as the tale goes, led to that fateful day at the bank.

Every participant in "The Dog" is a fascinating, authentically realized character in a way only the documentary format can provide. In addition to John Wojtowicz, there is first spouse Carmen Bifulco, who talks about her initial shock over her husband's criminal actions and her knowledge throughout their marriage that he was far from monogamous; John's adoring elderly mother, Theresa, who speaks frankly about knowing far more about her son than she let on back in the day; Liz Eden, who passed away from AIDS-related pneumonia in 1987, but is spoken about at length and seen in talk show archival footage, and John's institutionalized, developmentally disabled older brother, Tony, with whom he regularly spends time. Wojtowicz is full of wily vigor and audacious forthrightness in interviews, telling his personal version of the life he's led.

What directors Allison Berg and Frank Keraudren keep hidden until the very end of "The Dog" is when their interviews have been taking place. Watching them, the viewer assumes they are current—that is, until cancer and other health issues rear their cruel heads and our lead subject physically begins to wither away in front of the production's unflinching cameras. Other participants in the film have also passed since their interviews were shot, as revealed during end credits that, in a full-circle touch, are perfectly scored by Elton John's "Amoreena" (the song that so unforgettably opens "Dog Day Afternoon"). Impactful in ways that Berg and Keraudren could not have even guessed when they began the project in 2002, "The Dog" is born anew just as it concludes, an emphatic, unanticipated final layer to a picture not only about a wild life lived without regrets or shame, but about a whole interconnected web of souls whose existences, like all of ours, were entirely too fleeting.