Natasha Romanov, called the Black Widow, agent of S.H.I.E.L.D, rescues a young girl from Ivan, the man who once trained her as an assassin -- and eight years later she is called upon to protect the teenager Ava has become from a threat from the past -- and possibly from S.H.I.E.L.D itself.
Assassins -- Fiction.
Assassins -- Juvenile fiction.
Avengers (Fictitious characters) -- Juvenile fiction.
Secret societies -- Fiction.
Secret societies -- Juvenile fiction.
Superheroes -- Fiction.
Superheroes -- Juvenile fiction.
Young adult fiction.