Film-makers Joe Lawlor and Christine Molloy have a restless creativity and alertness to ideas which continues to be uniquely valuable. Now they have made a vivid, intense, true-crime drama about the inner life of the late Rose Dugdale, the wealthy English heiress and debutante who was radicalised at Oxford, joined the IRA and in the early 70s was involved in an art theft from a stately home in the Irish republic – and also helped drop homemade bombs from a stolen helicopter on to a police station.

Baltimore should really be seen in tandem with Lawlor and Molloy’s recent personal essay film The Future Tense about the film-makers’ own complex sense of evolving identities in Ireland and England, inspired by their own experiences making this Dugdale movie. With great intelligence and care, they make the most of a mid-range budget; a bigger Hollywood biopic would undoubtedly have given us Rose’s debutante ball at Buckingham Palace and the later bizarre helicopter attack as two big set pieces (perhaps with two star names in cameo for the royals in the ball scene). Instead, Lawlor and Molloy stage something that is smart and supple and more intimate: the heist scene with three other IRA men, with its chaotic and paranoid aftermath, intercut with moments from her own girlhood, presented as memories or fragments, equivalent in dramatic value to Rose’s nightmares and her terrified sense of what she still might have to do.

Imogen Poots is excellent as Dugdale, seen almost throughout in searching closeup, wondering whether she has it in her to execute a possible witness in cold blood. Tom Vaughan-Lawlor, Lewis Brophy and Jack Meade are strong as her conspirators and Dermot Crowley is outstanding as Donal, a gentle innocent bystander with fading eyesight, reading To Kill a Mockingbird in braille in his cottage as he receives a disturbing visit from Dugdale. An entirely absorbing, coolly low-key movie.

• Baltimore is in UK and Irish cinemas from 22 March