The scenes of migrating crabs on Christmas Island in the Indian Ocean would not have been out of place in a nature film. But in this, her first longform documentary, Gabrielle Brady contrasts the phenomenon with a very different kind of migration. We see idealistic trauma therapist Poh Lin visiting the island’s heavily guarded Australian detention center for illegal immigrants, many of whom have been held there for many years without any prospect of release.

The camera calmly observes Poh Lin’s conversations with the detainees, and these scenes are juxtaposed with other observations of the tropical island to create an intuitively composed metaphorical mosaic. Conservationists come to the aid of the crabs, while the local Chinese community is preoccupied with the wandering ghosts of workers who died there a hundred years ago.