Following a gruesome night of terror, a newly-orphaned young girl named Henrietta is taken under the wing of a secret Italian agency. The Social Welfare Agency is in the business of altering the minds and bodies of children like Henrietta to become assassins. It is up to Henrietta's 'fratello' -- or 'sibling' -- named Jose to show her the ropes... and keep her delicate mind from spinning out of control.

Worried that a mistake during her most recent assignment will alienate her even more, Henrietta tries hard to find her place at the agency. But Jose feels responsible for Henrietta's shortcomings, and it's up to him alone to find out what his 'fratello' needs to make her the best assassin the Italian government owns.

For the first few years of her life, Rico was trapped in her own body, completely unable to move. But two years ago, the Social Welfare Agency stepped in and gave her a body she could move all she wanted -- as long as she followed the agency's orders. Happy with her place in the world, she meets a resilient boy named Emilio while scoping out a new mission. And it's his fresh attitude that begins to turn over Rico's ideas of who she is supposed to be.

The Hilshire-Triela fratello head to Naples in search of Mario Bossi, an infamous criminal long since retired. Their mission is to find and protect Mario, even against his wishes. Reason: many people want him dead -- He's a government witness in a case against organized crime. But the friction between Hilshire and Triela might be too much of a struggle for the fratello as they try to concentrate on their mission.

Captain Raballo is a former Military Policeman who, after suffering a leg injury, was forced to resign. When Jean approaches him to join the agency as a Handler in return for re-instatement in to the MP, he jumps at the opportunity. But when he's teamed up with Claes, he soon realizes that his selfish needs are not worth the pain he will put the young assassin through.

Known terrorist Enrico Berdini is planning a major attack on Rome, and Jose and Henrietta are on the case with Rome Branch's Enzo. Together they are tracking Berdini, who is negotiating a deal to buy an explosive device from two of the best bomb makers in Italy for the attack. Once the deal is done, the Agency will move in to neutralize the threat.