How do you make a film about someone of whom there exists no moving images? Diving into the mysteries surrounding Leonie Brandt, an actor turned double-agent for the Dutch intelligence service during the second world war, Annette Apon’s documentary enlists the extensive archive of the Eye Film Museum, an approach that unfortunately obfuscates rather than illuminates a historical enigma.

Depicting the “greatest hits” of Brandt’s life, from her brief acting career to her daring exploits in Nazi Germany, the film utilises a wide range of clips mostly from silent movies, the images edited together as literal illustrations of the events recounted by the voiceover. There’s little stylistic purpose here, as the film oscillates between the first-person POV of Brandt and Apon’s third-person perspective. For cinephiles who know their film history, to see footage featuring such recognisable faces as Asta Nielsen used as visual signposts of Brandt’s biography is less than helpful. Sandwiched between these sequences are restaged excerpts of a 1995 interview between a lawyer called Besier who was acquainted with Brandt during the postwar years, and an unnamed researcher. Under these unnecessary layers of artifice and re-enactment, the real Leonie Brandt sadly recedes further into the shadows of the past.

Apon’s curiosity seems to stretch no further than Brandt’s own words and Besier’s recollections. Her film, for example, constantly reiterates that Brandt’s espionage activities all stemmed from her love for acting. While the performance aspect of intelligence work is certainly noteworthy, spying is more than child’s play. What about Brandt’s political beliefs? Why did Brandt write so glowingly of her (supposed) encounter with Hitler?

In mythologising Brandt into a romantic but empty cliche of a failed actor who simply cannot stop acting, this flawed portrait is more interested in iconising rather than fleshing out an undoubtedly complex personality.

• Leonie, Actress and Spy is available from 9 June on True Story.