Plot

Two young boys, Valerio and Christian, form a powerful friendship over the summer.

Rome, 1976. Valerio is ten years old and has a lively imagination. His life as a child is turned upside down when, with his mother Gina, he witnesses an attack on his father Alfonso by a terrorist group. From that moment on, fear and a sense of vulnerability leave a dramatic mark on the feelings of the whole family. But it is precisely in those difficult days that Valerio gets to know Christian, a boy not much older than him. Solitary, rebellious and shameless, he seems to have appeared out of nowhere. That meeting, in a summer filled with discoveries, will change their lives forever.—Canon y mus

In the beginning, we see two men meet at the subway station after the train service was interrupted and everyone has to evacuate. Then we go back to 1976 when these two men met as young boys. It says it's inspire by a true event.

Valerio(Mattia Garaci) hides food and brings it to an imaginary friend in a hiding place in the building and plays a game until he sees his dad, Alfonso(Pierfrancesco Favino) is coming home. He is living with his parents and a younger sister, and gets lots of love and attention, but still feels lonely.(hence the imaginary friend) One morning, he wakes up from the noise and witnesses a gunfight in front of his house. His young mind can't process the magnitude of the incident, but remembers the face of a gunman bleeding to death. Then we see him back to the hiding place, but everything's gone including his imaginary friend. Then he learns about the gunfight and his dad is involved. But when the dad comes home from the hospital, everything seems back to normal.

Valerio is back to school but gets bullied from the boys who know his father's reputation. Then he meets Christian(Francesco Gheghi) while playing in front of his house with a football his dad gave him. Next day, he ditches school and explores the town with Christian. They steal money from the church then Christian invites Valerio to a tree where he lives. We learn that Christian is an orphan and a homeless. Two boys come back to the place where he saw the dying man and Valerio explains what happened with a chalk drawings. However his parents alerted by school came back to find him and realized that their son saw everything. Valerio remembers that his dad was shot as well as the gunman who shot his dad got shot by other gunman who came together.

Valerio's family leave the city and hide at grandparents' in a country side. They are greeted by their extended family, but Valerio was left alone at the beach one day. Then he meet's Christan. He said he came to see him and they hang out together again. Valerio put Christian in a hiding place and bring him food just like he used to do to his imaginary friend. They become blood brothers. Valerio's parents find out about Christian's presence, and much to their surprise, the allow him to stay if not reluctantly. They even take him to the family gathering. Christian is envious Valerio's close-net family and it causes awkward tension between the two boys. Finally it erupts on a boat trip with dad, and Christian got almost drowned. Feeling guilty for pushing him into water, Valerio awaits Christian and finds out he's the son of the dead gunman whom he witnessed. Valerio goes after Christian to the cliff, and his father finds him the last minute and Christian disappears.

Back to the present time, grown-up Valerio and Christian meet again at the subway station and they explore the city together.