On 3 January, Israeli tanks attacked the area where Sana and her family lived. Their house - like Shifa's - was located close to the border, not far from a pretty, gold-domed mosque and a graveyard. Shifa Salman's family managed to flee. But Sana's family - her mother says - were blown to "pieces of meat". It is left to Sana's grandmother to recount the story, while the girl and her mother listen. She tells how a rocket hit the house, injuring Fida with shrapnel. She quickly bled to death. The father told the family to flee in their donkey cart, but a second missile exploded, fatally injuring him, too. I listen as Sana's grandmother describes how in the smoke from the explosion the weeping mother found her son Ibrahim "missing half his face". The family gathered what they could of their dead in a blanket and took them to a neighbour's house, where they were trapped, sitting with the bodies, for five days.
I had heard about Sana in January, from Dr Fadel Abu Hein at Gaza City's Community Training Center and Crisis Management. Fadel was sending teams of social workers and therapists to run workshops for the most badly affected children, even working with them as they sat on blankets in the rubble. As we talked about the types of trauma suffered by children during the conflict, he mentioned a girl who had seen most of her family die and had spent days trapped with their bodies. I had met her the following day, at the house of an uncle she was staying with. And I had tried to talk to Sana then. But sitting on a bed in a cold, bare basement room, she had been withdrawn behind a wall of grief, managing to speak barely a handful of words. Instead, it was the other relatives who had crowded the room who supplied answers to my questions. The only thing I learned was that she liked to paint, and so I had bought her pens and paper, since all of hers were lost.
Sitting in her new flat, Sana fetches the only drawing she says she has done since the killing of her brothers - in charcoal grey, against a shaded blue background, are the names of the boys. A day later, I learn from Nahid Hanrarah, the social worker who has worked most closely with Sana, that she has done other paintings, paintings of her family drenched in blood.
"Painting their names is an improvement," Nahid says. He adds that Sana is much improved, but when I ask her questions, she answers in fragmented sentences: "Things aren't too much better. Everything is still... I feel things are separate. The anger and the sadness. The one who could make us happy [Sana's father] is the one we've lost."
There are long pauses when Sana looks away. "People have tried to help me. There have been people at school ... " Sana mentions her irritation at those among her friends who insist on trying to talk to her about what happened on 3 January and in the days that followed. "I feel I can't concentrate at school like I used to," Sana explains. "I hate it because people at school keep asking how my family died. They think if I talk then it will help me. That is why I went to see Nahid. Because it makes me so upset.
I don't want to talk about it." Sana is also scared to go to the bathroom alone and, she tells me, she suffers with nightmares. I learn from talking to Nahid that Sana was suicidal when she was first referred to him. "She didn't want to live. She had no hope," he explains quietly.
It has not only been at school where Sana has been confronted by what happened. At home, too, she has had to deal with constant reminders of her loss from her mother, Laila, whose grief is even more debilitating.
"I think," Nahid suggests, "that Sana is the only one in the immediate family who really understands what happened to them, and who can help the family. Her mother can't do anything, really. So the responsibility has fallen on Sana. Sana is growing [as a person] from the knowledge of all the things that she passed through, which is helping her to overcome. But it is a process that is far from complete. They were a family of nine, now only four are left."
There are moments when you see an echo of how this family must once have been. Before the Israeli soldiers came. Before the war. Malak crawls on to her mother's knee with her doll and squeals loudly: "Bite her! Bite her!" Suddenly I realise that Sana is smiling at her mother. It is the first time in five visits to this family that I have seen her smile. And when she does, another girl is briefly visible.
And Sana is smiling again when I next see her. We are talking about ordinary things other than the horror that befell her; about the films she likes to watch - Bollywood and action films, X-Men - about her new computer, and the internet connection she is waiting for with excitement: "Before, we didn't have a computer. I've had it two weeks." Then the pain is in the room again. "The first thing I'm going to do is put pictures on it of my father and my sister and my brothers."
She seems sad, but not unreachable. I ask Sana if she will be going to the beach in the holidays, but it is her mother who answers: "We used to go to the sea, all of us together. We don't go any more ... " There are ghosts in the room that Laila cannot ignore. And because Laila cannot ignore them, Sana is also bound to observe them, and to mirror her mother's grief.
Laila says she has nothing left, and I remind her of Sana and Malak. She looks up at the pictures above her. "Rakan was the most beautiful," she sobs, as Sana begins to cry, quietly. "He was only four and a half. He was a very naughty boy. People kept saying to his father: 'This boy will be someone.'" When his sister went to carry him, I did not recognise him. He had come to pieces."
In Dr Fadel's office, decorated with pictures of dead Palestinian fighters, he tries to assess what has changed and what has not. Some people have begun to rebuild their lives, while others living in tents, or displaced, or living - like Shifa's family - among the ruins remain largely in the circumstances they were in when the war ended. "The biggest obstacle that we are facing is among those people whose problems have not ended - who live in a continuing war atmosphere. Nothing is happening about the destroyed homes, because we live in a continuing state of economic siege. So there are people still living in tents, or in the rubble."
Visiting his office one day I am confronted with evidence of how those dealing with damage from the conflict can progress. Hanging on one wall are pictures drawn by trauma-affected children, before-and-after images whose real subject is the effects of exposure to violence, and how it can be mediated. The "before" pictures show soldiers with guns, tanks and jets, images of destruction and death. The "after" pictures show the ordinary stuff of childhood: flying kites and images of family and friends and flowers, produced after lengthy work with the centre's social workers.
I mistakenly believe that they come from the recent conflict. I am informed that they pre-date the war - describing the experience of Israeli military incursions and air strikes. When I ask to see drawings produced after the January war I am led to another series of sketches that depict - so far - only fighting. And examining them, I am reminded of another picture I had seen a few days before in Khan Younis, in Gaza's south, in a child's bedroom.
I had first encountered Rewa'a Omer, aged 30, in the Nasser Hospital, standing between the beds of her two children, her daughter Ola and her son Yahya. It was a few days after the ceasefire and Rewa'a was clutching a bloody piece of clothing. An hour or so before, 10-year-old Ola, and Yahya, nine, had been standing close to their school gates with a group of other primary school children, waiting for a lift to take them home. As they stood chatting, an Israeli drone had fired a missile at a passing Hamas fighter on a motorbike three metres from the children. The blast had driven shrapnel into the legs of the children and a sliver into Yahya's eye.
Until I see the poster in Ola's bedroom, I think she has recovered better than her brother. It depicts a baby's smiling face. But someone has drawn trickles of blood coming from the nose and mouth, and added small scarlet cuts. Rewa'a tells me it was Ola who had disfigured it. I notice, too, that she has shaded around the baby's eyes so that the skin appears yellow. I think of how her brother's face was in his hospital bed, bruised under the bandages and stained with something like iodine.
Rewa'a's family are what passes for middle class in Gaza. Her husband was a police captain in the Palestinian National Authority before Hamas's assumption of full executive power in 2007, at the end of the most violent period of the so-called "internal fighting" between Fatah and Hamas. He does not work now but still receives his salary. Well-educated, Rewa'a speaks excellent English.
The family asks me for a copy of the photograph I took on the day the children were injured, and Rewa'a shows me an image saved on her phone, given to her by a neighbour, that shows her son being carried from the scene in someone's arms, his head limp and bloody. "It was on the television. And I was not there to protect them."
There are still some marks on her daughter's legs, like dark bruises. "My son was injured worse," she says. "He is still shy about wearing shorts because of the scarring. There was shrapnel in his eye that we did not know about. He had to go to Egypt to be operated on. They have recovered physically," Rewa'a adds, "but emotionally my daughter is more damaged than my son. That first time that she saw her brother bleeding has stuck with her. I think it will always be inside. She talks about what happened and her grades at school have suffered. It was a month and a half before she was ready to go back to school."
Rewa'a says that Ola is still frightened to go to the bus stop, and "the children are always fighting now. I worry all the time about them, waiting for them to come home from school."
Ola wants to tell the story of what happened to her. "The car was late. There was a sound and I woke up and everything was black. Things were broken and bleeding. Then people came to rescue my brother. Someone took my hand. I said: 'My brother! My brother!'" I ask Ola what she would like most. She does not have to think about it: "I would like to live somewhere safe."
Yahya wants to talk about Egypt, where he went to have the shrapnel taken from his eye.
"I went to the zoo and saw the pyramids!"
"I feel that there is nowhere safe in Gaza any more," adds Rewa'a. "I used to think before that ... you know, we are ordinary people. This [the violence] had nothing to do with me."
When I visit Rewa'a again we climb up on to the flat roof of their building. Fading home-made kites are propped in tangles of string against the balustrade. Rewa'a seems oppressed by the thought of what has happened. "I wish that they could have a normal childhood. I didn't grow up in Gaza, I grew up in Saudi Arabia. I came back to Gaza when I was 16. I had a beautiful childhood. I want the same for them. Not this.
"Every time the summer holidays come round I wish there was something that they could do. Hobbies that could help them grow. But there is nothing here like that." I remind her of something that Yahya told me when I asked what he wanted to be when he grew up. He replied that he wanted to be a fighter. "Yahya says that. But it is just an idea in his head."
As we are leaving I ask Rewa'a if she has any hope that things might change in Gaza. She seems sad. "Nothing ever changes. There is no rebuilding. Everything becomes worse.
Nothing here ever changes for the better."