'This book is about a symobiotic relationship. It tells the story of a Bobtail squid and the bacteria that help it glow in the moonlight.

First we meet Ali, an intrepid Vibrio fischerie bacterium determined to reach safety. Then we meet Sepio, a baby Bobtail squid who is still unable to glow. His dark shape is too obvious in the moonlit water and all kinds of predators lurk nearby. Can Ali and Sepio help each other? What kind of dangers do they face? What can we learn from their adventure?' (Source: Back cover)