The film's four characters remain nameless, appearing to be generic symbols.
The Boy, whom the narrative centers on, is neglected and abused by his parents who treat him like an unwanted nuisance. They literally bark, growl, and crawl on all fours, symbolizing their distance from being human. All of the actors are caked with white powder makeup that causes their skin to glow brightly amidst the ultra-high contrast photography. The Boy's only attire is a black tuxedo with a bow tie, which combined with his solemn, pain-stricken face suggests he is attending an eternal funeral. Perhaps the Boy is dressed for his own funeral, because his life appears to be 'dead' on a symbolic level. The Father always wears a stained, moth-eaten white undershirt with equally dreadful boxer shorts. The photography is so high contrast that you often only see the Boy's stark white face and hands 'floating' around the pitch black background. On the opposite spectrum, the Father's bright clothes appear to jump out of the darkness, making his presence dominant and obvious.
Despite the abstractness of The Grandmother, several themes appear evident. The Boy expresses the loneliness and pain that accompanies a household with abusive and neglectful parents. The Grandmother character, who the Boy secretly grows from a plant-like seed in the attic, symbolizes warmth and comfort. The Boy both figuratively and literally 'grows' a parental figure, comparing the growth of love to that of a plant. The Boy's actions suggest that love should be treated like growing a plant: you first plant the seed, then nurture it until it matures into something full and complete.
After much attention and care, the Boy's plant grows into a massive, pulsating cocoon out of which the Grandmother crawls from, fully clothed and aged. The Boy and Grandmother immediately embrace and offer each other much-needed comfort. His world seems brighter for the time being, but his living nightmare is far from over. Ultimately, nothing lasts forever, as this film appears to suggest.
The Grandmother is highly recommended for fans of the avant-garde, or anyone looking for something different. If you thought Eraserhead was Lynch's darkest and weirdest film, wait until you see this small miracle.