In January 1993, UK Parliament passed the controversial Mutant Registration Act, mandating that all mutants must disclose their genetic status. When Claire Cavendish, the headteacher of Avalon Institute, publicly refuses to register her status. This act of defiance attracts the wrath of the government who send a specialised military unit to manage the situation in the Scottish Highlands. As Avalon finds itself besieged they witness a country slowly spiralling into chaos as ‘Robin Hood’ and his Sherwood Rangers launch a campaign of terror.

To force a break in the stalemate Claire allows herself to be arrested and gets put on trial, leaving behind a tense situation with those staff left behind in the institute and the Genetic Oversight Unit laying siege to the ancient bastion.