Whencurious blue rays light up the sky over Cockermouth in a mysterious pattern,young sisters Mae and Isla Donaldson face shape-shifting adversaries. With thehelp of their irascible Granddad, the girls discover how to break a secret codeand unlock the truth about a group of special agents who disappeared from aLake District beauty spot while investigating UFOs. The girls must prove theirsuspicions about the glamorous new people in town before it's too late.