Part love story and part political thriller, this observational documentary tells the story of Nazanin Zaghari-Ratcliffe - the British-Iranian charity worker who was arrested at Tehran airport in 2016.
Nazanin was about to fly home to London after a visit to her parents with her baby daughter Gabriella. She was charged with spying, separated from her baby, thrown into Tehran's notorious Evin prison and handed a five-year sentence.
Back in London, her husband Richard begins a relentless public campaign to get Nazanin freed and to discover why she was seized in the first place. He uncovers that her fate is intimately bound up in a huge British-Iranian arms deal for tanks from the 1970s that went wrong in the aftermath of the Iranian Revolution.
Five years in the making, this film has unprecedented access to Richard and little Gabriella - and to Nazanin herself in Iran - as the family struggle to bring her home.
Nazanin airs Thursday 16th March on Channel 4.