At last: one of the most staggeringly strange cases of Stockholm syndrome in history – and surely the weirdest story ever to have emerged from world cinema – now has been given the serious documentary treatment. In the 1950s and 60s, producer-director Shin Sang-ok was the titan of South Korean cinema, but by the 70s his career was flagging. In North Korea, the dysfunctional communist princeling Kim Jong-il was obsessed with movies and conceived the bizarre notion of jump-starting his nation’s film industry by abducting Shin to work for him. This he did by instructing an agent to pose as a producer, luring Shin’s ex-wife Choi Eun-hee to Hong Kong with the promise of a role, kidnapping her and taking her to North Korea. The reason? Bait. He calculated, correctly, that Shin would come looking for her in Hong Kong – where he too was abducted. (It begins to sound, bizarrely, like the plot of The Vanishing.)

They were imprisoned separately but finally brought together by Kim, and in a grotesquely abusive situation compelled to remarry as the golden couple of North Korean cinema and for seven years allowed remarkable freedom to make western-style commercial films of the sort Kim yearned for. Eventually, they were allowed to visit European film festivals where they finally made their escape – but found they were widely disbelieved, precisely because of this apparently happy and productive professional renaissance. Their story here is riveting, although, as so often with this kind of material, I would like a clearer signpost as what has and has not been historically reconstructed.