I feel like I missed something with this. So, apparently the rainbow serpent has taken a modern guise as a bus picking up the stupid and the isolated to lure them in and digest them. I think I remember hearing of the rainbow serpent before, an Australian legend I guess?
But beyond that, I feel like I missed something. It revealed pretty early on that the serpent was the bus, didn't it? So I'm not sure what happened beyond that, of note. The unmarked shifts in time didn't help as I tried to reorient myself again between the present of Gavin riding the bus, the past of Gavin's argument with his ex, and the far past of the rainbow serpent's history.