The Q Continuum is an extradimensional domain in which Q and others of his kind exist in immortality. Although immensely powerful and intelligent, they require the stimulus of novelty to maintain their vitality hence their interaction with other species.
While the Enterprise struggles to survive an alien onslaught, Captain Picard has been kidnapped by Q and taken on an astounding journey back to that immeasurably distant moment when the Continuum faced its greatest threat. But far more is at stake than simply the mysteries of the past, for an ancient menace is stirring once more, endangering the future of the galaxy, and neither Q nor Starfleet may be able to stop it.