Penelope Greensmith is a bio-librarian, responsible for a vast seed bank made possible by the mysterious Vice she inherited from her father.

She lives a small, dedicated life until the day the enigmatic and charming Horticulturalist arrives in her garden, asking to see her collection. He thinks it could hold the key to stopping a terrible plague sweeping the universe.

Soon Penelope is whisked away on an intergalactic adventure by the Horticulturalist, experiencing the vast and bizarre mysteries that lie among the stars.

But as this gentle woman searches for a way to save the universe, her daughter Lily is still on Earth, trying to track her down, and struggling to survive the terrible events unfolding there...