Guy's 'Sis' is played by Maya Lawson by the way.
The father (all of this is symbolic/metaphor) uses the family signet ring (multigenerational abuse families [this is supposed to be semi-autobiographical] leaving their "brand upon the brain".) to extract 'Nectarite' from his daughter and the orphans' skulls, leaving suspicious imprints on the back of their heads (so obvious metaphor, penetrating their brain [general MK/messing with their heads symbolism]).
Together with his teenage sister and a horde of orphans, young Guy Maddin [coming back to the island triggers these long-ago dissociated memories; imaginitive games (pretending to be the 'Lightbulb Kids') that children would play, the characters they constantly read/obsessed over (shows how the programming of alters can be manipulated through controlling their environment, what they read/watch) would became both siblings' alter-personalities ([alters can be either sex ((hence all the androgyny here)), they're sometimes not even human ((not hard to do, simple dehumanization methods))] their minds escaping together in this 'detective' alter-reality ((survival mechanism, allows them to forget all the bad things they themselves have experienced as they are a different person, and find out what actually happened)); the scenes of Chance kissing the sister and such are actually acts of incest between the brother and sister, the mask, top-hat, "The Undressing Gloves" are all part of this too)] lazes away his under-stimulated youth on the mysterious island he will someday inherit. In the lighthouse orphanage in which they all live, their every move is watched over by their overbearing and tyrannical mother while their father, a scientist and inventor, works away secretively in the basement.
When new adoptive parents discover mysterious head wounds on their children, teen detectives Wendy and Chance Hale - brother and sister sleuths known as the "Lightbulb Kids" - visit the island to launch an investigation [this description takes a lot of things far too literally; these are fictional characters ((like the Hardy Boys)) that they read as children so to find out what really happened ((and other, more primal and psychosexual reasons)) they would dissociate into/become the characters/personalities they know so well (through reading)]. Guy is weak-kneed as he falls for Wendy, while Sis is flushed with love for Chance, a love which must be kept from Mother at all costs. As the investigation progresses, the kids are led into the darkest regions of revelation and repression as the terrible secrets of Guy's family are revealed.