Babbs and her twin brother Boston travel the universe through Doors, with a capital D. They can step through an intergalactic Door and come out anywhere on any planet. The Doors have always been exciting for the twins, until it all goes wrong. Now their grandmother has disappeared through the Doors, they've accidentally unleashed the dreaded fearmonger monster on the earth, and they must fix everything while keeping their adventures secret from the powerful, intergalactic Doorkeepers-the Order of the Porters. The twins find help from Friz, a six-legged alien who looks strikingly like a cocker spaniel. Together the three friends explore the darkest, loneliest places in the universe, testing their courage and searching for clues. But they must keep their cool. If they attempt to use the Doors in a state of fear, they could end up transported to the galactic abyss or worse.