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.
The barrier has been broken and Q's oldest enemy is free once more. Captain Picard and his crew find themselves in the middle of a cosmic war between vastly powerful entities. The future of the Federation may be at stake, but how can mere mortals intervene in a battle of gods? Picard has to find a way, or he may never be troubled by Q again.