Two years ago, Train, a high-level assassin known as Number XIII in Chronos, left the secret society to live by his own rules. Since then, Train has been a sweeper, a bounty hunter, catching criminals and bringing them in alive. But his main mission is to find a former Chronos member who killed his best friend.

Train Heartnet changes from an assassin to a bounty hunter; and Karl ask for Train's help in catching a serial killer with strange powers.

Train Heartnet, reformed assassin turned bounty hunter, also known as Black Cat, comes to the aid of a troubled boy seeking revenge for the death of his parents and is forced to confront his own vengeance-laden past. Meanwhile, Rinset forms a shaky new relationship with an old enemy.

Somehow, the past has placed a sixty billion double dollar bounty on Vash's head, and the gunslinging pacifist can't seem to get away from money grubbing citizens with itchy fingers.

The Apostles of the Stars try to convince Train's doctor to join them, risking his chances of returning to normal size.

"Years after the fall of the Galactic Empire, a solitary bounty hunter is given a simple mission. Find and return the Child to the Imperial Remnant, all that remains of the once all-powerful Empire. This mysterious orphan has a power that can possibly turn events in their favor, and acquisition of that power is paramount. Instead, the bounty hunter goes on the run with the Child to protect him from the forces that would do him harm. Here is the story...

Follows the crew of the spaceship Bebop--ex-gangster Spike Spiegel, ex-cop Jet Black, amnesiac Faye Valentine, genius child Ed, and the dog Ein--as their work as bounty hunters places them in the midst of a mafia battle.