The intergalactic adventure starts at home with Harriet, who discovers that her hearing-aid can do more than she ever bargained for when she finds an alien in her room. Discovering that her family secretly work for an intergalactic agency, Harriet becomes the Earth's first line of defence as the only one who can understand the invaders. Sure, her hearing aid helps her understand aliens from across the universe, if only she could understand her own feelings.