Raised by her father (Eric Bana) in the Finnish wilderness, teenage Hanna (Saoirse Ronan) has trained all her life to be the perfect assassin. Her father sends her on a mission, and she stealthily makes her way across Europe while evading agents sent after her by a ruthless operative named Marissa (Cate Blanchett), who once worked with Hanna's father. As she draws closer to her target, Hanna faces startling revelations about her existence and begins to question her humanity.