That is the most nauseating of other brutal moments in this obnoxious film from bad boy von Trier, who has called this the most important film of his life. That’s his problem. For kicks, try watching the scene in which the troubled lady drills a bar through her husband’s leg and attaches a weight on the far end to prevent his pulling it out.

What’s going on here? Grief has turned a couple into raving maniacs, and they wind up going at each other in primal scenes that turn the film into a horror show. The trouble is that one cannot care much for either of them, leaving the film a self-indulgent filmmaking atrocity. Von Trier has said that the work stems from a depression he suffered. Better he had confined matters to a psychiatrist than exorcizing whatever demons he had for an audience to endure.

The course of the film is a pity, for there is a very promising lyrical opening. While the couple, played by Willem Dafoe and Charlotte Gainsbourg make love, their baby son, Nic (Storm Acheche Sahlstrøm) escapes his confines and manages to get over to a window, from which he tumbles to his death in slow motion. He (Dafoe) is a controlling person who tries to manage She’s increasing despair of guilt at the tragedy. She begins to resent him and his smugness. (Not naming the couple is a shopworn device to bestow symbolic weight and universality.)

The relationship gives way to growing paranoia on She’s part, with He trapped in a vain effort to control if not ease her pain. Step by Step the film escalates into a thoroughly batty onslaught of personal destruction. It is as if a Bergman film had gone bananas. But writer-director von Trier is no Bergman. His “Breaking the Waves” was the best of his works that I have seen, but “Antichrist” is sheer provocation.