Emily Blunt, Rebecca Ferguson and Haley Bennett are already on board the project.
It centres on Rachel (Blunt), a woman who is jobless and an alcoholic and, who spends her daily train ride fantasising about the seemingly perfect couple living in a house that she passes.
She begins to realise that she may have witnessed or been involved in a crime, after she comes home one night covered in blood and is unable to remember much from a blackout drinking episode.
Bennett is set to play Megan, a married neighbour with whom Rachel's ex is having an affair and who goes missing.
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Evans, 34, would play Tom, the ex-husband, and Leto, 43, would play the neighbour's husband, but sources say one stumbling block to an eventual deal is scheduling for both actors, said The Hollywood Reporter.
Tate Taylor is directing the project, which has a script by Erin Cressida Wilson.
Marc Platt is producing the film, which will be executive produced by Jared LeBoff and Celia Costas.
Leto next stars as the Joker in Warner Bros' anti-hero superhero movie, "Suicide Squad". Evans just wrapped shooting "Captain America: Civil War".