One of the main criticisms fans had with the casting of Emily Blunt was that she was too attractive for the role of a broken and chronic alcoholic Rachel Watson. The makeup artists got around this by extensively studying the skin of actual alcoholics and applying makeup to make her look more exhausted and washed out with dark circles under her eyes and puffy cheeks. The fact that Blunt was pregnant during filming helped with the effect.
Emily Blunt was at the beginning stage of pregnancy at the start of filming. She kept this from the cast and crew except for her friend, co-star Justin Theroux. Director Tate Taylor only found out of the case towards the end of filming when, filming a scene of Rachel showering, he noticed her bump and confronted her, asking if she'd withheld information he should have known. Blunt eventually had to tell him and he agreed to keep it secret. By the time filming ended in February 2016, she was in her fifth month of pregnancy.
The book that this film is based on is actually set in England, and Rachel Watson gets the train into London. Emily Blunt is from London, England. For this film, the location was changed to New York but Rachel speaks with Emily's natural British accent in keeping with author Paula Hawkins' vision.
The painting that Rachel Watson is looking at in an art gallery is "The Subway" by George Tooker. In real life, this painting is in the collection of the Whitney Museum of American Art in New York City. When Tooker died in 2011, his New York Times obituary called him a "painter capturing modern anxieties"--certainly an apt expression of Rachel's state of mind at the start of the movie.
The novel debuted at No. 1 on The New York Times Fiction Best Sellers of 2015 list and remained in the top position for fifteen weeks, thirteen of which were consecutive. The book had sold more than 3 million copies in the United States alone as of July 2015.
During the audio commentary the director informs us that the psychiatrist's home is an actual Frank Lloyd Wright house in New York. It looks much like one of his buildings in the Usonia section of Pleasantville, NY.
There are many similarities to Alfred Hitchcock films such as The Lady Vanishes (1938) [the missing woman], Rear Window (1954) [a character sees a murder happen across a distance from a window], Psycho (1960) [the girl in the shower] and Vertigo (1958) [the girl in the museum looking at the painting].
On September 21, 2015, this was reported that Jared Leto and Chris Evans were in talks to join this film, where Evans would play Tom Watson, Rachel's ex-husband, and Leto would play the neighbor's husband.
In the novel Rachel has an affinity for gin and tonics mentioning Schweppes being her preferred brand of tonic water. In the film Rachel is seen pouring what looks a bottle of vodka with the Schweppes logo into her water bottle.
At about 16 minutes into the audio commentary the director mentions the village of Croton (on Hudson), home to the historical Croton Dam. Locals will tell you that below the dam on the banks of the Croton River, Hollywood filmed the classic Tarzan movies starring Johnny Weissmuller with suburban Westchester County standing in for the African veldt.
The scene at about 18:50:00 where an aerial shot shows the train passing the home of Megan and Scott uses CGI to transpose 8-9 homes from Macy Ave, Westchester, NY - 8.7 miles NW to wetlands on the bank of the Hudson River near Freemont Pond in Sleepy Hollow, NY. The exterior shots passing the house each way must have been filmed from what was previously the fairway of the now-defunct Ridgeway Country Club.
The trivia items below may give away important plot points.
The writer of the online article Rachel reads describing the discovery of Megan's body is "Elizabeth Roderick". Elisabeth "Betty" Broderick was an affluent suburban housewife convicted of murdering her ex-husband and his new wife. There are multiple similarities to the film: She was born in Eastchester, NY (the film takes place in Westchester, NY). Much like Rachel's husband in the film, her husband had an affair with an employee, later divorcing his wife and marrying his mistress. He accused his ex of being mentally unstable. She would call repeatedly and harass the new couple, leaving hundreds of obscene and profanity-laden messages on Dan's answering machine. She ignored countless restraining orders forbidding her from setting foot on Dan's property and often showed up a their house uninvited and drunk. She vandalized his new home and even drove her car into the front door despite the fact that their children were inside at the time. Ultimately, she entered the home one night and shot the couple to death.
In this film Rachel Watson is infertile, but Emily Blunt was pregnant during filming. This also occurred during filming of Into the Woods (2014) in which Blunt, pregnant in real life, plays a character who cannot get pregnant.