At dawn, Sarah Linden sprints hard through the woods. In a nighttime flashback, a frantic teenage girl also races through the trees, gasping as she crouches to elude her pursuer's flashlight beam.
Back in the present, Sarah receives a phone call and rushes to a crime scene, where she follows a bloody trail of evidence to a surprise going-away party thrown by her peers. It's Sarah's last day as a Seattle homicide detective.
Sarah returns home, where her fiance, Rick Felder, is about to fly to their new home, in Sonoma, California. Sarah and her 13-year-old son, Jack, are to join him that evening. "I do want to marry you," Sarah tells Rick.
At the police station, Sarah meets her replacement, Stephen Holder, then receives a final assignment from her boss, Lieutenant Oakes, who tells her to bring along Holder. During their drive to the crime scene in Discovery Park, Holder recounts his eight years as a narc for the county police.
An officer at the park shows Sarah the evidence so far: a bloody pink sweater and Stanley Larsen's ATM card. Because there's no body, Sarah says sex crimes should take over the investigation, but Holder wants to check out Larsen.
Moving-company owner Stan Larsen makes a midday stop at home to fix an oft-broken dishwasher. His wife, Mitch, broaches the subject of their daughter, Rosie, attending college out of state. "Gotta let her grow up sometime, Papa," says Mitch.
Meanwhile, Darren Richmond, a Seattle city councilman and mayoral candidate, stands quietly before an outdoor mausoleum. Later, upon arriving at City Hall, Richmond lies to campaign manager Jamie Wright and lead advisor Gwen Eaton about where he's been, then announces to his staffers that Councilwoman Ruth Yitanes will endorse him, which could seal an election victory.
Sarah and Holder visit the Larsen home, where Mitch says that she and her husband spent the weekend camping out of cell-phone range. Sarah notices a pink bicycle in the garage and asks Mitch if she has a daughter.
At Fort Washington High, Sterling Fitch fires off an urgent text to Rosie: "CALL ME 911!" Sterling later tells her teacher Bennett Ahmed and Principal Meyers that Rosie spent the weekend with her. Bennett accuses Sterling of lying.
Back at the Larsen home, Mitch tells Sarah and Holder that Rosie went to a Halloween dance on Friday. Her daughter said "only freshmen wore costumes" and wore a pink sweater. Mitch takes a call from the school and learns that Rosie wasn't with Sterling over the weekend and hasn't been seen since the dance.
Back at Fort Washington, Richmond and his rival, mayor Lesley Adams, are about to address a student assembly. At Sarah's request, Richmond cancels the assembly so the police can investigate Rosie's disappearance. An irritated Adams makes it clear to Richmond that he's aware of the impending Yitanes endorsement.
Sarah and Holder question Bennett, who describes Rosie's sexy Halloween costume. With a leer, Holder asks if Bennett agrees that Rosie is a "pretty hot piece."
"I wouldn't know; she's 17," Bennett replies.
Sarah receives a call from her son's school and departs. Meanwhile, Sterling slips off campus to a tweaker hangout, where a boy named Kris hints that Rosie hooked up with another teen, Japser Ames, who'd scored some ecstasy and "was definitely out to bone."
At his parents' stylish vacation home, Jasper ignores his cell phone while playing a video game. In a nearby bed, a moaning woman knocks over a glass and breaks it.
Sarah drives to a marina and drops off Jack, who was suspended from school for smoking cigarettes. Jack refuses to be consoled about the impending move and reminds Sarah that Rick isn't his dad.
At their apartment, Stan asks Mitch about "that rich jack off," referring to Jasper. He and Rosie broke up, Mitch responds.
Crime dogs at Discovery Park pick up and then lose Rosie's scent; Sarah orders another sweep, which Holder maintains is unnecessary. He's chastened when an officer reports that a possible burial site has been found.
At campaign headquarters, Jamie presses Richmond to capitalize on Rosie's disappearance, but the candidate refuses to cooperate. Rattled that Adams knew about Yitanes, Richmond asks Jamie and Gwen if a staffer is leaking information. Not long after, a female staffer phones Richmond regarding a reporter's inquiries into a rendezvous that only she, Richmond, Jamie, and Gwen know about.
Stan confronts Sterling, who blurts out that Rosie is with Jasper. Stan calls a relieved Mitch, and Oakes halts the investigation. Sarah, still skeptical because no one has spoken directly to Rosie, remains at Discovery Park, but when the suspected burial site yields only a doll she declares, "We're done."
Stan bursts into the Ames' weekend home. Ignoring Jasper's protests, he charges into the bedroom, only to find a middle-aged woman in the bed.
Still at Discovery Park, Sarah notices three girls with fishing poles walking along a fire road and wonders where they're headed. Holder speculates there could be lake nearby. As night falls, a crane hoists a black car out of the lake.
Stan calls Mitch to tell her that Rosie wasn't at Jasper's house and that he's now heading to Discovery Park, where the pink sweater was found. Still on the line with Mitch, Stan approaches two police vehicles blocking the road. He's too far away to see anything when Sarah has the retrieved car's trunk popped. The body of a teenage girl is found inside.
"You can't be here," Sarah tells Stan, but her face confirms his suspicion that Rosie is dead.
"No!" he screams as Mitch listens helplessly.
"Ran the plates," Holder informs Sarah. "Car belongs to the Richmond campaign."
As police photograph the body, Sarah notices the girl is wearing a butterfly necklace that Mitch mentioned. At dawn, Sarah Linden sprints hard through the woods. In a nighttime flashback, a frantic teenage girl also races through the trees, gasping as she crouches to elude her pursuer's flashlight beam.