It was a bizarre happening: a Brooklyn bank robbery on a hot August afternoon turned hostage crisis, with one of the thieves admitting that he did it to pay for his transgender bride's sex-change operation. Film fans know the story from Sidney Lumet's gritty 1975 classic Dog Day Afternoon. But there is much more to this ripped-from-the-headlines tale and to John Wojtowicz, the robber whose antics inspired Al Pacino's Sonny Wortzik character. The Dog employs archival footage and contemporary interviews to separate truth from fiction to get to the heart of Wojtowicz's story. Combat experience in the Vietnam War radicalized this former Goldwater Republican, while an affair with a fellow soldier clarified his sexual orientation. Upon his return to Stonewall-era New York, he threw himself into the nascent gay rights movement. Decades before gay marriage was a cultural flashpoint, Wojtowicz married Ernest Aron, a.k.a. Liz Eden, in a public ceremony. That much is true and so are the bare facts of the robbery, but separating fact and legend with such a slippery character can be tricky. Wojtowicz is disarming, funny, and seemingly frank, but also the very definition of an unreliable narrator. While his mother (a pistol), two of his wives, and others fill in some of the details, it is Wojotwicz's voice-whether describing his outrageous sexual exploits or revisiting the scene of the crime-that dominates. Ten years in the making, Alison Berg and Frank Keraudren's lively documentary captures the essence of Wojotwicz and his times.