A man with the ability to enter people's memories takes on the case of a brilliant, troubled sixteen-year-old girl to determine whether she is a sociopath or a victim of trauma.

In a dystopian near future, single people, according to the laws of The City, are taken to The Hotel, where they are obliged to find a romantic partner in forty-five days or are transformed into beasts and sent off into The Woods.

In the near future or an alternate reality, there are memory detectives, people who have the ability to enter other peoples' electronically aided memories. They often are used to resolve psychological conflicts, and sometimes to exonerate someone from a crime. John was at one time the top in this field but he has been recovering from the death of his wife, and a stroke. To get back into work the head of the small firm he works for offers him what is supposed to be a simple job, getting 16 year old Anna to start eating again. However, the "simple job" turns into his most challenging.

Hanna (Ronan) is a teenage girl. Uniquely, she has the strength, the stamina, and the skills of a soldier; these come from being raised by her father (Bana), an ex-CIA man, in the wilds of Finland. Living a life unlike any other teenager, her upbringing and training have been one and the same, all geared to making her the perfect assassin. The turning point in her adolescence is a sharp one; sent into the world by her father on a mission, Hanna journeys stealthily across Europe while eluding agents dispatched after her by a ruthless intelligence operative with secrets of her own (Blanchett). As she nears her ultimate target, Hanna faces startling revelations about her existence and unexpected questions about her humanity.