A SIMPLE FAVOR
*CUT TO THE CHASE*
This spoiler was submitted by Jeremy
The film starts with Stephanie Smothers (Anna Kendrick) making a video for her mom vlog, "Hi Moms!" Before she begins with her recipe, she updates viewers on an ongoing case involving Stephanie's best friend Emily Nelson (Blake Lively), who has been missing for the last five days. Stephanie appears to start crying before composing herself to give new viewers a recap on what has happened.
It started when Stephanie went to her son Miles's (Joshua Satine) school. Stephanie is always volunteering and contributing to Miles's class, to the point where some other parents like Darren (Andrew Rannells), Sona (Aparna Nancherla), and Stacy (Kelly McCormack) think Stephanie is making them look bad. After school, Miles wants to have a playdate with his friend Nicky (Ian Ho), Emily's son. Stephanie meets Emily when she goes to pick Nicky up, and, at the boys' constant requests, Emily agrees to the playdate and invites Stephanie to come over for drinks.
Stephanie arrives at Emily's stylish home. She is stunned to see a nude drawing of Emily hanging on the wall. Emily is blunt and rather crass, even telling Stephanie to stop apologizing. She works for a fashion company as a public relations manager. Stephanie is a widow after her husband and brother died in a car accident. The two have martinis and trade secrets. Emily tells Stephanie of how she and her husband, one-time author Sean Townsend (Henry Golding), got into a threesome with Sean's teaching assistant. Stephanie then tells a secret of how, after her father passed away, she met a son he had from another relationship named Chris (Dustin Milligan). In her grief, Stephanie turned to Chris, and the two wound up having sex, leading Emily to call Stephanie a "brother fucker". Sean arrives home and meets Stephanie while he and Emily make out passionately. Stephanie says she has read Sean's book and enjoyed it. However, when Sean isn't there, Emily notes that Sean hasn't written a thing since the first book, and that they are close to bankruptcy.
While taking the boys to the park, Stephanie snaps a picture of Emily for the school's yearbook. Emily firmly orders Stephanie to delete the picture because she doesn't like having her picture taken.
Emily calls Stephanie and asks her "a simple favor" to pick up Nicky from school because she has to take care of some work business, while Sean has gone to London to look after his injured mother. Stephanie obliges, but after two days, Emily hasn't come for Nicky. Stephanie calls Emily's job and is told that Emily flew to Miami to handle something, which she didn't mention to anyone, even Sean. Stephanie gets in touch with Sean to inform him, and he returns home for Nicky, and they speak to the police regarding Emily's disappearance.
Stephanie takes it upon herself to find out what happened to Emily. She goes to Emily's job and meets her overbearing boss, designer Dennis Nylon (Rupert Friend). Afterwards, Stephanie sneaks into Emily's office and finds a black-and-white picture of Emily with "Gotta have faith" written on it. Stephanie is spotted on her way out of the office and Dennis threatens her, but Stephanie remembers hearing Emily speaking brashly to Dennis, and Stephanie hits back with some sass of her own to get Dennis to back off. Stephanie then uses the picture of Emily to make flyers.
After a few days of Emily being gone, one of Stephanie's vlog viewers sends her a message stating that Emily may have been spotted in Michigan driving a white car. Authorities go by a lake where the car was spotted, and sure enough, they fish the car out of the lake, as well as Emily's body. Sean is called in to identify the body, and he breaks down.
A funeral is held for Emily. Nicky and Miles get into a fight when Miles says that Emily is in Heaven, and Nicky yells at Stephanie, claiming that she's trying to be his new mom. After the reception, Stephanie and Sean console each other, which leads to the two of them having sex.
Stephanie is met by Detective Summervile (Bashir Salahuddin), who tells her that Sean took out a $4 million life insurance policy on Emily before she died. It's also said that Emily had heroin in her body at the time of her death. She goes by the school where Sean works and sees him getting very friendly with his teaching assistant. Growing suspicious, she asks Sean about the life insurance, which Sean says was Emily's idea after learning that Stephanie lives off her husband's insurance, so they were thinking about Nicky in case something happened to either of them. He also tells Stephanie a story about the ring that was found on Emily's finger. It belonged to his mother, and although Emily claimed she had given it to her and wanted Emily to have it, Emily actually made it look like it was lost and that she just found it. They would later go into the airplane bathroom where Nicky was conceived.
Shortly after, Sean convinces Stephanie to move in. As Stephanie takes out Emily's clothes from the closet to her put her own clothes in, Stephanie is startled to see all of Emily's items placed in their same spots. At home, Nicky claims to have seen Emily, who told him to say hi to Stephanie. Later on, Nicky gives Stephanie an envelope that he says is from Emily. Stephanie opens it and finds a picture of Stephanie with her family and Chris, with "brother fucker" written on it.
Stephanie continues to dig into Emily's history. She takes the nude portrait of her and tracks down the artist, Diana Hyland (Linda Cardellini), who was once in a relationship with Emily, but she used the name Claudia. Diana says Emily was a con artist who scammed her out of money after she paid off her student loans and college debts, and then she disappeared completely. Diana then gives Stephanie the one thing she kept from Emily, which is a T-shirt for a bible camp called Squaw Lake.
Stephanie visits the camp and gets old books with pictures from past campers. She finds many pictures of twins Hope and Faith McLanden. After contacting numerous people with the name McLanden, Stephanie manages to find Hope and Faith's mother, Margaret (Jean Smart). Stephanie disguises herself as a cleaner and then sits down to ask Margaret about her daughters. She describes the two of them as being trouble, especially Faith. Stephanie shows Margaret the picture she found in Emily's office and confirms that the woman in the photo is Faith. It turns out that when Hope and Faith were 16, they burned down the east wing of their home with their father inside, and the two vanished without a trace.
Now that she's onto something, Stephanie makes a video calling out to Emily, forcing her to reveal herself as being alive. Emily meets with Sean at the restaurant they always go to on their anniversary. Emily expresses her disdain that Sean had sex with Stephanie in their home, and appears to threaten Sean with a gun, only to pull the trigger and reveal the gun wasn't loaded.
Emily meets Stephanie in the cemetery by her own grave. Emily tells Stephanie her side of the story, although a flashback reveals what Emily ISN'T saying. Emily, who is really Hope, and her twin sister Faith burned the east wing of their house with their father inside because he was abusive. She notes that she is actually a triplet, but their sister Charity died in the womb. After the fire, they ran away from home and planned to meet up elsewhere, but Faith never showed up. 16 years later, Faith contacted Emily to meet up at the camp, where Emily found that Faith has become a heroin addict. Faith tried to blackmail Emily, and Emily drowned her in the lake and used her body to be found so that Sean and Nicky can get the life insurance money since they were broke. However, despite Emily stating that Faith's death was a suicide, Stephanie knows it was murder. Emily then accuses Stephanie of not being fully honest regarding her relationship with Chris, implying that he is Miles's real father. A flashback shows that Stephanie's husband Davis (Eric Johnson) was also suspicious as well, and that he took Chris on the car ride that ended their lives. Additionally, Emily plays a recording of her conversation with Sean in the restaurant, where he says that Stephanie meant nothing to him and that he thought of Emily during sex.
Stephanie then brings in an insurance lawyer, who tells Sean that since it was discovered that Emily had a twin, the insurance company is hesitant to pay the full amount, especially since it is a large amount of money.
Emily steals a wrench and tosses it into the air so that it hits her in the eye. She walks into a police station to make it look like Sean beat her and forced her to fake her death, as part of a scheme to frame Sean for insurance fraud. Sean is investigated and later taken into custody but released on bail.
Stephanie then plans with Sean to get Emily to confess to the murders of her father and sister. Stephanie comes in with a gun and pretends to shoot Sean, but Emily already knew of everything and cut the mics that the police planted. She takes out her own gun and shoots Sean in the shoulder for real while also confessing to the murders. Stephanie then reveals that she has a hidden camera on her blouse, and that her viewers have all seen Emily's confession. Emily attempts to escape as Stephanie goes after her. Emily draws her gun on Stephanie, but she gets slammed by a car driven by Darren. Moments later, the police arrive to arrest Emily.
Six months later, Stephanie's vlog has hit one million viewers. She continues to provide recipes and home remedies, while also aiding the police in investigations.
Ending text states that Stephanie's vlog continues to bring in viewers, while she has also started a part-time detective agency and has helped the police solve at least 30 cases. Sean has written another successful book and has gotten a job working at another university, and he still lives with Nicky. Emily was sentenced to 20 years in prison, but she has adjusted to prison life nicely, as she is seen playing basketball with her inmates.