I pounded myself against the inside of his head, but it was useless. He couldn't hear me; I was trapped. So, like any other prisoner, I waited. I bided my time.

Luke is six. He is a lonely child, but he has one friend, his best friend - Daniel - whom he met in the playground on the day his parents finalised their divorce. Only Luke can see Daniel. They play games together, and Daniel watches over Luke; he is there when he first wakes up and there when he goes to sleep. Daniel's first memory is of Luke calling his name in the playground. Daniel is not an ordinary child.

Luke's mother spends more and more time in her room, haunted by family memories. She takes Luke and Daniel from New York to a deserted beach town, as winter sets in. Daniel is changing. He feels faint, weightless. Luke seems forgetful of him.

Time passes. Luke and Daniel have not seen one another for a long time. Until, one night, Daniel suddenly finds himself standing in Luke's bedroom, woken by the sound of breaking glass. He does not know how much time he has; but he knows how he can be saved.