Seattle homicide detective Sarah Linden is partnered with Stephen Holder, a transfer from county narcotics, to investigate the case of Rosie Larsen, a teenage girl who disappeared after attending a school dance. A car is pulled from a lake in Discovery Park; Rosie's body is in the trunk. The vehicle is registered to the campaign of Darren Richmond, a Seattle city councilman who is running for mayor against incumbent Lesley Adams.
Rosie's parents, Stan and Mitch, have no idea who harmed their daughter. An early lead focuses on Rosie's wealthy ex-boyfriend, Jasper Ames, and his pal Kris Echols. Suspicion intensifies after video surfaces of the two boys performing lewd acts with a girl in the high school's secret basement party room on the night of the dance, but it's revealed that the video is a fake, and the girl in the video is Rosie's best friend, Sterling Fitch, not Rosie.
Jamie Wright, Richmond's campaign manager, and Gwen Eaton, Richmond's campaign adviser (and secret lover), urge Richmond to use the case to generate voter sympathy by linking Rosie's untimely end to his own wife's death in a drunk-driving accident. Richmond refuses.
Gwen introduces Richmond to Tom Drexler, a wealthy local entrepreneur with a grudge against Adams. Drexler donates $50,000 to Richmond for a media blitz.
In need of cash to cover the costs of Rosie's funeral and the mortgage on a house he purchased to surprise Mitch, Stan gets a loan from Janek Kovarsky, a mobster he once worked for.
One of Rosie's teachers, Bennet Ahmed, becomes the prime suspect after Holder connects Rosie to an after-school hoops program where Bennet volunteers and Sarah discovers letters from Bennet in Rosie's bedroom.
Bennet tells Sarah and Holder that he was at his apartment when Rosie stopped by to return a book on the night of the dance, but a video proves that Bennet was at the school. Bennet's wife, Amber, tells Sarah and Holder that Bennet's friend Muhammed Hamid has a key to their apartment.
Richmond begins airing a commercial promoting the hoops program that prominently features Bennet. During a televised debate, Adams reveals that Bennet is a murder suspect and hammers Richmond for coddling criminals.
Stan's friend Belko Royce tells him that the police are investigating Bennet. When Bennet shows up at Rosie's wake, Stan offers to drive him home but instead brings him to a dock, though he releases Bennet unharmed.
Adams outmaneuvers Richmond at a City Council meeting, getting Richmond's program defunded. Drexler brags to Jamie about having dirt on Adams.
Sarah and Holder's search for Muhammed brings them to a downtown meat market, where they become ensnared in an FBI anti-terrorism raid. While inside, Sarah spots a pink T-shirt that Mitch later identifies as belonging to Rosie.
Sarah becomes suspicious of Holder after seeing him receive an envelope of cash and follows him to what turns out to be a Narcotics Anonymous meeting, where she learns about his junkie past.
Richmond approves going public with the dirt on Adams provided by Drexler: the mayor got a teenage intern pregnant. Adams denies the affair.
Holder has a wiretap placed on Bennet's phone and tells Sarah that a judge friend of his can issue a warrant for arrest. In a wiretapped conversation, Bennet and a caller discuss passports and "the girl."
Sarah prepares to arrest Bennet, but the judge refuses to sign the warrant. The detectives catch a break when Amber provides Muhammed's cell-phone number and they use his phone's GPS to track him down. Muhammed reveals that the conversation wasn't about Rosie but rather a Somali girl he's trying to help.
After Mitch accuses Stan of letting Rosie's killer get away, Stan and Belko kidnap Bennet. Stan beats Bennet, unaware that there is evidence proving the teacher is innocent. Upon learning about it, Stan surrenders to the police.
Video from a cab places Rosie inside the Larsen apartment after the dance. Belko, who, unbeknownst to Rosie, was in the apartment when she stopped by, recalls overhearing Rosie say, "Adela, I'll be there." Sarah discovers that a local ferry named Adela has a late-night departure for a casino whose logo matches the key chain found with Rosie's body.
Sarah requests a warrant to review the casino's ATM footage but becomes distracted when her son, Jack, goes missing. Sarah and Holder spend the day searching for him.
ATM footage places Rosie, made-up and wearing a low-cut blouse, at the casino. The footage leads the detectives to Beau Soleil, an escort service. Rosie's Aunt Terry tells Sarah and Holder that she occasionally works as an escort and describes hearing another escort's tale of a john with the pseudonym "Orpheus" discussing a drowning scenario similar to Rosie's.
Sarah obtains Orpheus' e-mail from the Beau Soleil database and e-mails him. While visiting Richmond, she sees the e-mails to Orpheus on Richmond's computer. Richmond catches her looking at his computer.
As the detectives seek more evidence against Richmond, rumors surface about his affairs. Richmond issues a public denial but confesses to Gwen that he dated several women after his wife's death.
After hearing that Stan has reconnected with Kovarsky, Mitch refuses to post bail, but Terry does so.
Holder directs Sarah to a gas station whose attendant describes hearing a girl screaming on the night Rosie disappeared. The police search a nearby forest and turn up Rosie's sneaker.
Sarah visits Richmond again and accuses him of murder. Gwen overhears her and withdraws the alibi she previously provided. After Holder produces a tollbooth security-camera photo of Richmond driving the car that Rosie's body was found in, Sarah arrests him.
Stan returns home. "Every piece of this place hurts me," Mitch sobs. Later that evening, she leaves her family.
Sarah receives a call from highway patrol: the tollbooth cameras have been off-line for weeks. The Richmond photo is a fake. Elsewhere, Holder gets into a car and tells an unseen driver, "Photo worked. He's going down."
As police escort Richmond to a car, Belko approaches Richmond and pulls out a gun.