Harry, a 8 year old boy from a small island called Guernsey in the British Channel has been assigned a pen pal for the summer. Simon, a 9 year old boy from London, who has been assigned a pen pal for over the summer. What happens when the two send letters back and forth for years on end, going through things together, and never alone. Will the two men get on? Or will they be a squabbling mess?