The artist is apparently going mad. He sits up night after night, staring into his candle, speaking with his wife of his strange dreams (or are they memories?). Bergman penetrates the man’s subconscious to extract a series of bizarre nightmares and imaginations. He slips these hallucinations back and forth across the line of reality, so that occasionally what seems to be a dream becomes gruesomely real. This is the case with the most powerful image in the film, an act of necrophilia that becomes a practical joke.
Much of the film retains Bergman’s ability to obtain deeply emotional results with very stark, almost objective, scenes. One night the artist tells his wife of a time when he was a child. He was shut up in a dark closet and told by his parents that a little man in there would eat his toes off, in terror, the child began climbing up on shelves, and boxes, begging to be released.
Another night, the artist tells of a day when he went fishing at the seashore and was joined by a small boy. We see this scene in heavily contrasted black and white: There is a moment when the boy stands behind the man and could push him onto the rocks below, while the man compulsively winds in his fishing line. A moment later, in a fit of rage, the man kills the boy. The question is, did either of these scenes occur, or were they both nightmares? Bergman does not quite let us know.
-- Roger Ebert (1968)