The story is being told by an old fish to her children and grandchildren about a Little Black Fish who, tired and dissatisfied with his life without any purpose in a small brook, decides to venture out in search of the sea and to learn about life in other parts of the world.
At each phase of the journey he sees something new, faces threats, acquires awareness and is proud of his wise decision. In one part small fishes join him, but when caught in the pelican's pouch, they blame him for having tricked them; and beg the enemy to let them kill him in exchange for their lives.
Later he meets a wise lizard, who encourages him to not be afraid, arms him with a small dagger to use whenever he is in danger, and tells him about a team of fishes who have joined forces and work together to save themselves whenever they are caught in fishermen's nets.
The Little Black Fish finally reaches the sea and decides to join the team of fishes; thinking about what he has accomplished:
"I might face death any minute now! But I should try not to put myself in harms' way as long as I can live. Of course, it is not important if I die, because this will happen anyway. I know my purpose, my purpose is: how will my life or death impact the lives of others."
A seagull catches The Little Black Fish, he sees a tiny fish inside his stomach, cuts a hole with his dagger and saves him before saving himself.
The grandmother and all others sleep. But a Little Red Fish could not close her eyes even for one second. All through the night she was thinking about the sea.