Actor/director Bill Paxton just proved something to the world. He’s proven that a film doesn’t need endless blood and gore to make an audience squirm. He pieces together a picture that’s smart, vile, disturbing and, at times, terrifying. Together, all of these qualities make “Frailty” (Lions Gate Films, R) a top-notch thriller packed with an ending that makes a second viewing irresistible.

“Frailty” begins with Fenton Meeks (Matthew McConaughey) approaching FBI agent Wesley Doyle (Powers Boothe) with information pertaining to a serial killer calling himself “God’s Hands.” Not only does Fenton tell him that he knows who the killer is – he tells him it’s his own brother, Adam.

The film uses flashbacks as Fenton tells the rest of his story. We’re sent back to the summer of 1979, when 12-year-old Fenton (Matthew O’Leary) and 9-year-old Adam (Jeremy Sumpter) are awakened late at night by their father (Bill Paxton), who tells them about a dream he had. Apparently, an angel appeared to him, telling him that his mission from God is to destroy demons that live in society as humans.

But this means killing people, and young Fenton wants no part of it. However, the younger, more impressionable Adam immediately jumps on the bandwagon and pledges to help his father carry out “God’s Will.” The rest of the film is pretty much a guessing game of who’s rational and who isn’t. The ending is a bit much, but Paxton executes it so magically that it works.

“Frailty” couldn’t be released at a more disturbing time. Watching it, one can’t help but be reminded of Andrea Yates (the Texas mother who drowned her children, claiming afterward she did it because Satan ordered her to). If Yates really believed this, is she not guilty of her crimes? If Fenton Meeks’ father really believes he’s on a mission from God, is he really guilty of murder, as Fenton tells him he is? Or did God really choose him to carry out this mission? “Frailty” will have audiences asking all of these questions while sitting on the edge of their seats, waiting for the answers.

This may very well be the best performance of Bill Paxton’s career. In today’s modern world, his character’s rants about the wrath of God and the coming apocalypse ordinarily would have audiences seeing him as a complete nut. However, Paxton’s performance is so convincing that audiences will find it hard not to believe him.

The real star of this show is neither McConaughey nor Paxton, but young newcomer Matt O’Leary. How Paxton got a performance out of a child actor that’s this riveting, this bone-chilling, this spectacular, is anybody’s guess. If Haley Joel Osment impressed audiences in “The Sixth Sense,” O’Leary’s performance in “Frailty” will blow them out of their seats.

After seeing this film, one could ask Bill Paxton a single question about his directing skills: Why have you waited this long to use them? This is the first time Paxton has directed a film in his 25-plus years of working as an actor in Hollywood. Only a director with a talent like his could make such a complicated plot feel so understandable.

The transitions between past and present that editor Arnold Glassman executes are some of the best in years. Glassman’s editing, Paxton’s directing and astonishing performances make “Frailty” one of the best films audiences will see this year.