Werner Herzog has always been preoccupied with what he refers to as the “ecstatic truth” – for him, “The deepest essential that defines us as human beings.” This has never been more evident than in his recent documentary work. Of these features, the remarkable triad of Grizzly Man, Encounters at the End of the World and The Cave of Forgotten Dreams stands out for its conspicuous attempts to lay bare the essence of the human soul; his latest, Into the Abyss, proves to be a very worthy companion piece.

The film charts the fallout from a triple homicide committed in Conroe, Texas in 2001 and consists of interviews with everyone in some way involved, including killers Michael Perry and Jason Burkett, as well as police footage of the crime. As the gory details are pored over, a comprehensive portrait of both a senseless crime and a troubled society emerge. What is already an intrinsically tragic story is given an extra edge by the knowledge that the interview with Perry takes place just eight days before his eventual execution.

In Herzog’s capable hands, what could have been another tear-soaked sob-story with a clear humanist message is, in fact, so much more. Throughout his interviews with a broad array of characters including the victims’ families as well as the perpetrators themselves, the director’s balance and open-mindedness guard against any clear agenda to the film. It is not a tedious diatribe against capital punishment; the indefensible is not defended, merely questioned. Herzog, though morally against capital punishment, is more interested in the lack of meaning in life and the cruelty of the world.

The world of Perry and Burkett is the brutal milieu of lower-class, semi-rural Texas: a place where drug-taking, violence and retribution are ways of life. In an interview, Burkett’s father – himself a former drug addict in prison for life – admits that his son “never had a chance”, tearfully recounting how his impassioned testimony saved his son from the lethal injection. Despite the bleakness on show, itself oddly in tune with the director’s own existentialism and nihilistic worldview, there is also much humour on offer – not all of it gallows-related.

Almost every slow-motion shot and swell of violin is counterpointed by muffled laughter. Some of it comes from the unusual line of questioning often pursued by Herzog, as when he asks the priest, with a chuckle, to “Please describe an encounter with a squirrel.” Other instances are derived from the sheer absurdity of the circumstances his interviewees find themselves in and the ragtag cast of characters he encounters, never short of a mind-boggling anecdote or plain-talking sense.

There are, of course, surreal Herzogian flourishes: such as the executioner who suddenly gave up his job and pension after an epiphany, the image of the stolen car for which four men ultimately died, weed-ridden and abandoned in a police lot, not to mention the mysterious pregnancy of Burkett’s wife, whom he married whilst behind bars and with whom he has never had physical contact.

Given the nature of the crime and approximation of the motives presented by the director, no clear explanation or examination of the root of evil is offered. We are simply left to ponder whether the abyss of the title is the death so prominent in the documentary, or actually life in our broken world. Nonetheless, for a despair-drenched documentary dealing with death, the film also manages to be a paradoxical celebration of life, where the resilience of humanity is exalted. No matter how adverse the situation, people continue to live their lives with what dignity they can muster. A masterful movie, it remains an essential watch either way.