Thirteen-year-old Theo has been home-schooled since he was ten, but his mother's terminal illness forces him to enter Year Nine at his local state school. Struggling to fit in, he reluctantly agrees to join a national pen pal project.

His letter lands on the desk of Alexander —a confident, upper-middle-class private school boarder, gifted classical musician, and aspiring county rower—everything Theo is not. Despite their differences, the two boys begin to secretly confide in each other, sharing their struggles with grief, loneliness, and the pressures of a society that is demanding conformity.

As their correspondence blossoms over three academic years, Theo realises he has fallen for the boy in the letters. Concerned that the world around him remains unwelcoming, and with their schooling coming to an end, Theo must step out of the shadows and express his feelings before he and Alex miss their final chance to meet.