After discovering that Happyhead was a sinister eugenics experiment, Seb along with a select group of participants, finds himself washed up (literally) on an isolated island called Elmhallow. Here the teens are split into two groups - the chosen Ten and the Bottom Percentile.

With the boys divided, Seb's burgeoning relationship with Finn is put to the test and when the competition takes a deadly turn, their plan to take down HappyHead rapidly unravels ...