Just as 18-year-old Londoner Erin sets off to spend summer in Israel with her best friend, Eliza, she unearths an old diary belonging to her seriously ill grandfather, Len. Intrigued by the life of this old man she barely knows, she takes the diary with her, and is stunned to learn of his part in the post-WWII British peace-keeping force in what was then Palestine.

Erin finds it hard to deal with the aftermath of the suicide bombing and the parallels with her grandfather's story. She decides to visit Eliza's grandfather to get some answers, though they may be uncomfortable.

Len discovers the source of the leak to the Jewish militia, with tragic consequences. Erin becomes even more determined to resolve the mystery surrounding the fate of her grandfather and his friend Mohammed as she continues to read his diary and embarks on a mission to absolve Len's guilt.