Sam is a teenage royal rebel, second in line to the throne of the kingdom of Illyria. Just as her disinterest in the royal way of life is at an all-time high, she discovers she has super-human abilities and is invited to join a secret society of similar extraordinary second-born royals charged with keeping the world safe.

When an evil spirit known as Pitch lays down the gauntlet to take over the world, the immortal Guardians must join forces for the first time to protect the hopes, beliefs and imagination of children all over the world.