A 16 years old teenager, Hanna Heller (Saoirse Ronan) stays with her father, Erik Heller (Eric Bana) in Finland. Since she was 2 years old, Erik has trained Hanna to be a killer. When Hanna states that she is ready, she gives a signal to tell her location where she has been lived along this time to CIA. Meanwhile, Erik goes first in order not to get caught by the CIA. The mission of Hanna is to kill Marissa Wiegler (Cate Blanchett).