Fire of Love remembers Katia and Maurice Krafft - a French volcanologist couple whose passion for volcanoes is only matched by their love of each other.
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In France, science and romance often go together. Pierre and Marie Curie bonded over radioactivity, and before that, chemists the Lavoisiers fell in love as they investigated combustion.
Oceanographer Jacques Cousteau managed to conduct bigamous marriages with two scientific colleagues.
So the story of Katia and Maurice Krafft, the stars of Fire of Love, shouldn't come as much surprise.
I knew virtually nothing about Katia and Maurice until I went to Fire of Love, but by all accounts, they were celebrities in France for the same reason as the Cousteaus. They converted their passion for vulcanology - the study of volcanoes - into movies and TV documentaries.
And you can't deny that footage of volcanoes is endlessly fascinating.
While the Kraffts were nothing like as prolific as some TV scientists, their footage turned up anywhere that needed volcano coverage. They also wrote several books on the subject, using Katia's brilliant still photography.
And the appeal was simple. They got closer than anyone else, and all their best shots are in Fire of Love.
But the story behind these literally death-defying shots is unexpectedly sweet. Maurice and Katia met early - both come from the same region of Eastern France - and realised immediately they were of one mind. They lived for volcanoes.
She'd been inspired by Mt Etna, he'd got the bug with Mt Stromboli. And from then on they would travel the world, looking for erupting volcanoes.
Maurice was the playful one. That's him doing volcano puns about their relationship - lots of "eruption" gags.
Katia was the more reflective one. She wrote the books, and when she wasn't acting as Maurice's unpaid model getting close to the torrential rivers of lava, she'd be taking the even closer photos.
You find yourself wondering which one was the crazier - or at least the most foolhardy.
For the first half-hour, I was prepared to give the biscuit to Katia, chortling beside a terrifying, red-hot fountain of magma, protected only by the wafer-thin, silver material of a sort of heat-proof parka.
But then Maurice put his hand up and set out in a rubber dinghy across a lake filled entirely with sulphuric acid. Katia, who's a chemist, told him not to be stupid - a clear case of pots and kettles, I'd have said.
When I tell you that the other item on Maurice's bucket list was to canoe down a mountain on a stream of molten rock, you'll see the Kraffts didn't dream like the rest of us.
The appeal of Fire of Love is how calm, sweet and - yes - romantic it is.
The narration is by performance artist Miranda July, no stranger to eccentric affairs of the heart herself with films like Me and You and Everyone We Know.
Director Sara Dosa's theme seems to be that love is strange anyway. So why should the love of two people who spend most of their lives climbing erupting volcanos be any stranger?
One thing I learned from Fire of Love is there are basically two kinds of volcanoes. There are the spectacular "red" ones, offering the scarlet rivers of liquid rock and explosive fountains of the stuff. And there are the "grey" ones, which will kill you.
Mount St Helens was one of those, with an explosive power many times greater than the Hiroshima atom bomb.
Needless to say, Katia and Maurice couldn't wait to go there. For them, an event like that was date night.