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.
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The episode begins in 1940s Palestine, where Len meets Abu-Hassan Mohammed, an Arab charwallah working for the British Army. Len is appalled to see how Mohammed is treated by some of the soldiers as he attempts to serve tea, so he intervenes to discipline them. A friendship grows between the two men after the incident.
Len is lying in hospital, being treated for his injuries after his unit has been under attack in Haifa. When he recovers, he goes to see Mohammed and spends some time teaching his son Hassan geometry. Len also visits his Jewish lover Clara before rejoining his unit. The soldiers prepare for a highly sensitive military operation against the Irgun, but their secret plans are betrayed, with appalling consequences for Len and his men.
In the final episode, Erin refuses to abandon her quest to find Mohammed's family, even though it takes her on a hazardous journey into Gaza.