The Spanish illustrator Josep Bartolí lived enough life to fill a dozen epic biopics. He fought against Franco’s fascists and fled over the Pyrenees into France with 500,000 other refugees in early 1939. After escaping from an internment camp, he made his way to Mexico, where he became a lover of Frida Kahlo. In New York, he was friends with Rothko and Pollock, and designed sets for Hollywood – until his name ended up on the blacklist. Now his life has been turned into a film: not an epic, but a slender and haunting French animation focusing on his years as a prisoner in France.

It’s the feature debut of Aurélien Froment, best known as a cartoonist for Le Monde where his work appears under the name Aurel. He frames the film with the fictional story of an elderly French man, Serge (voiced by Gérard Hernandez), who’s telling his grandson about his stint as a fresh-faced gendarme working as a guard at an internment camp. We see him as a young man (voiced by Bruno Solo), a gentle soul with a pleasant face. (He reminded me of a Raymond Briggs character.) His colleagues mock him for refusing to abuse prisoners, who are treated more like criminals than refugees. Secretly, Serge makes friends with one of the Spanish, a handsome man with a magnificent hooked nose, who is constantly drawing – scribbling pictures on cutlery, walls, in the dirt with his finger. He is Bartolí (Sergí Lopez).

Aurel draws scenes inside the camp in a grim camouflage of greys and dust browns, and shows us Bartolí’s angry, Goya-like drawings of the horrors: prisoners’ faces ravaged by disease and hunger, contorted with despair. Often the image remains still, the characters’ expressions and movements static – frozen like memories fixed in the brain after all these years. It’s a delicate, thoughtful film, moving and real. Not utterly bleak either, ending with a rampage of colour and life in Mexico – and a brilliantly sweary cameo from Kahlo.

• Josep is available on Mubi from 28 January.