Time
Time is the main motif of the novel. Time is essential in the sense of loss, inability to turn back time and make things undone, along with time in the sense of its passage correlating to different situations. For Stephen, time stopped at the moment he lost his daughter, and he still lives in her memory, or rather in imagination of her growing up. For Charles, he wants to go back in time, to when he was a child and to feel the safety and innocence of that time.
Memories
Memories are another important element of the plot-building. Stephen lives in the memory of his daughter, of her laughter, her scent, and her mannerisms. Inexplicably, he relives the memory of his parents' which will prove crucial to his own continuation of life. It is the memories of the past that help Stephen move forward and have new hope of a life together with his wife.
The sandcastle
A significant memory that Stephen has is the memory of building a sandcastle with Julie and Kate. The parents get seriously involved in the building of the castle that they, for a moment, forget their adult obligations. Kate announces several times that she wants them to live in that sandcastle and leave their old home. The sandcastle is important because it shows a child's ability to effortlessly focus all of their senses on a task at hand. Stephen thinks how powerful he would be if he could apply abandonment and intensity to everything as he did to that castle. Another reason the sandcastle is important is that it shows the child's ability to sense their parents' happiness with Kate's insistence that they start living there.
