Emily Blunt is helping to find her ex-husband's nanny in the official trailer for The Girl on the Train.

Based on Paula Hawkins' 2015 novel, the movie follows our offbeat and possibly untrustworthy lead (Blunt) as she witnesses something relating to the disappearance of the nanny (Haley Bennett) of her ex-husband (Justin Theroux) and his new wife (Rebecca Ferguson).

The Girl on the Train is directed by the helmer of The Help and Get on Up, Tate Taylor, and scripted by Men, Women & Children co-scribe Erin Cressida Wilson.

Luke Evans (The Hobbit), Édgar Ramírez (Joy), Allison Janney (Mom), Lisa Kudrow (Friends) and Laura Prepon (Orange is the New Black) round out the Girl on the Train cast.

Emily Blunt is best known for her roles in Into the Woods, The Devil Wears Prada and Looper. Last year, she played the lead in the drug crime thriller Sicario and played the villain in The Huntsman Winter's War released earlier this year. After The Girl on the Train, Blunt has voice work in the animated movies My Little Pony, Gnomeo & Juliet: Sherlock Gnomes, and Animal Crackers. In 2018, she takes on the iconic role of Mary Poppins in Disney's Mary Poppins Returns, a sequel to the original Julie Andrews-Dick Van Dyke musical.

The Girl on the Train is set for release on Oct. 7.