4.50 from paddington (2018)

Toko Amano worked as a detective, but to take care of her sick husband she quit her job. After her husband passed away, Toko Amano now works as a crisis management expert. 3 days ago, Toko Amano's former mother-in-law rode on an express train with beds. She witnessed a man strangling a woman and told the train conductor, but he thought she imagined it. The police later searched for the woman's body, but could not find her. Toko Amano boards the same express train that her former mother-in-law rode. She looks for the dead body.