As a boy, an 11-year-old Emerson is brought into the principal's office for the sixth time in ten days for beating on bully Guy Baxter. Psychologists couldn't figure out what was wrong with him. It turns out that Emerson is in love with Principal Swindle and acted up to be in her office. From that he learned that love is stupid.
Randy stops by to visit the Pie Hole and chats with Chuck. He's really there to see Olive. As they chat, Ted talks about love needing the right ingredients but Chuck insists that love is heartier. They admit they've been through a lot. They notice that Randy is leaving and Olive explains she's calling it off. Chuck talks with Randy, who explains that Olive just told him goodbye, shook his hands, and told him to leave. Olive has told him that she loved Ned but is over it and he believes it. Meanwhile, Ned talks to Olive who figures that she seeks out men who will abandon her. She decides to treat Randy as a rebound guy.
Emerson returns to his office to find Simone Hundin waiting for him. She's back from an animal training seminar and she assures him she won't be leaving him. Simone has found Emerson's pop-up book about his missing daughter, Lil' Gumshoe. She wants Emerson to be honest with her and hates being surprised. They're surprised when a woman comes in: Amelia Stingwell. Her brother Roland, a famous dam builder, has died and his rare jewel, the Dam Ruby has gone missing. Emerson hasn't seen her in nine years, and Amelia insists that Emerson should help for what happened then.
As it turns out, Roland Stingwell was last seen leaving after a busy day at the office. His body was discovered in a dry riverbed one half mile from the dam.
Emerson, Chuck, and Ned go to the morgue and discover that Roland's back was turned around 180 degrees. Roland knows Emerson and is surprised to see him. He accuses Emerson of stealing the love of his life and paying for it, but Emerson says he gave the money back and the woman he "took" wanted to be with him. Roland admits that now his anger is gone, but he could never make the woman love him. Emerson admits he never could either. With time running out, Roland tells them that Lila Robinson killed him, and Emerson explains that Lila is the woman who took his daughter.
Back at the Pie Hole, Emerson points out that he never told Ned because he would have told Chuck. Ned sarcastically points out they've never shared big secrets with him, and Emerson admits that it's complicated and Lila is an experienced grafter who has evaded him for years. Ned and Chuck offer their services to help find her and Emerson agrees to give it one more shot.
Years ago, Roland had hired Emerson to follow his fiancée, Emily Von Alastair. It turned out that "Emily" (Lila) was driving out in the woods to read Thoreau and bird watch. She spotted Emerson and they soon went on picnics together. Emerson hesitated and Lila told him that she was a grafter there to steal the Dam Ruby. Emerson returned the money to Roland and revealed Lila was pregnancy with his child. Roland swore to put Lila away if she ever was crooked again, and then went on to build the Papen County Dam.
The trio goes to the dam and tries to retrace Roland's steps. They meet with the guide, Taylor Philbean, and explain that they're there on the family's behest. Emerson explains that Lila eventually gave in to her criminal impulses and tried to steal the ruby. She couldn't find it and fled with her daughter Penny. As they go in, their photos are taken automatically.
Emerson and the others talk to Roland's secretary Trish, who admits that Lila met with Roland on the day of his death. The police were more interested in the contracts Roland were negotiating to redo all the pipes. The secretary notes that the local toxic factory has been dumping toxic wastes into the reservoir. Emerson notes a door to Roland's private exit, which leads through the damn to a stairwell. Emerson checks it out and finds police detective Puget checking out the same path. Puget points out there were plenty of people out to kill Roland. Emerson tells him to check out Lila and use everything he's got to catch her.
Back at his office, Emerson finds Simone waiting for him. She says she has something to tell him… and Lila steps out of the shadows, armed with a gun. She lied to Simone to get her there, and says that if Emerson clears her name, she'll let him see his daughter Penny. She tells him to hang a lantern in the window that night if he agrees. Emerson admits to Simone that Penny is his daughter. Simone figures Lila is lying, but Lila drugs them with horse tranquilizer before they can do anything
Simone goes to the Pie Hole to tell Ned and Chuck that Emerson is trying to clear Lila. She figures that Lila is lying, and Chuck insists that they help her. Simone prefers to go after Lila, and is upset that Emerson surprised her. Chuck goes after her. Meanwhile, Olive invites Randy back and apologizes for sending him mixed signals. Now she wants a fresh start. He asks if she plans to use him to get over Ned. Olive claims that's a crazy theory but Randy insists he doesn't want to be a rebound guy. Once he's gone, Olive tells a distracted Ned that she's dating Randy. He asks her if love can make someone do something crazy and she notes she went to a nunnery over him. Ned decides that Emerson needs their help and goes with Chuck.
After a day interviewing 28 farmers whose water was tied up by Roland's dam, they come to the 29th farmer, Michael Brunt. He offers flowers to Chuck and notes that if he wanted to kill Roland, he would have done it years ago. Emerson admits they don't have much and they're running out of time. They check the secretary's theory and talk to the Mennonite lawyers who work for the novelty company that is allegedly dumping toxic chemicals. Thanks to their commitment to truth, they tell them they did accidentally dump glow-in-the-dark chemicals once and will pay the fines. Ned suggests they send the police after Lila, but Emerson figures Lila could call an accomplice to send Penny to Mexico. He insists he'll do whatever he has to, even if Lila is lying and doesn't have Penny. Olive comes over and tells them they have to do something.
Olive goes to Emerson's office and finds Simone there giving the signal to summon Lila. Lila is there, but Simone has a gun and wants to talk. She figures Penny is a bluff: no grafter would keep a child. Lila admits she came back to see Roland but they talked things out and she gave back all the money she stole. She admits she grew a conscience: Penny. Lila goes for the gun and the two women struggle. Olive grabs it but drops out the cylinder. Simone manages to grab the horse tranquilizer but Lila runs out before she can use it. Once she's gone, Simone reveals the whole thing was a set up. Randy runs in and he and Olive go after Lila. Ned and Chuck have hid in the trunk of her car.
Emerson goes back to the dam and checks the photo machine. Puget is there and knows all about Simone and the Dam Ruby. Emerson tries to bluff but Puget points out there's also a photo of Lila leaving three hours later. He assures Emerson they'll have Lila in custody by morning, and then leaves. Emerson looks at the pipe schematics on the wall and gets an idea… and Simone arrives, figuring he'd return to the scene of the crime. She apologizes for bolting and he thanks her, and then leads her into the pipes.
In the trunk, Ned and Chuck discuss their relationship and Chuck admits that their love is hard. She wonders if it's worth it, particularly given what they can lose. Lila stops the car and opens the trunk, and tells them it's best not to talk when they're hiding in a car trunk.
Randy and Olive lose Lila and return to the Pie Hole with Olive. She admits she wanted to use Randy as a rebound guy but can't do it now. Olive warns that she'll be difficult but Randy admits that with him, she'll forget that she ever rebounded and he's willing to take the chance. They kiss and Olive is taken aback. Ned and Chuck come in, wearing only their underwear, and explain that Lila left them at the road and took their underwear. As they prepare to go after Emerson, they turn off the light and notice that the flowers from Brunt are glowing.
Emerson and Simone go to Roland's office and spot some more of Brunt's glowing flowers. The detective brings down the pipe schematic and shows that Brunt was getting free water because his farm is over the spot where the pipes are leaking. However, his water was contaminated, explaining the glowing flowers. Brunt came to deliver the flowers and kill Rollie, but overheard him talking to Lila. Brunt changed his plan, framed Lila, and took the ruby.
Simone wonders how there could be a photo of Lila leaving. Emerson takes Simone into the pipes and tries to come up with an explanation. Lila spots a woman dressed as Lila locking them in. The figure reveals himself as Brunt, disguised as Simone. Rollie hid the Dam Ruby before he died so Brunt came back to find it. He opens the water valve and runs. Emerson spots the Dam Ruby in a crack, and they spot the water pouring toward them. They run to the end of the tunnel and find themselves on a ledge. Fortunately, there's enough space to move to the aside and avoid the wash of water. Emerson realizes the water pushed Roland a half mile away.
The facts are these: as Brunt locked Roland in, Roland hid the jewel in the crack and was then swept out to his death. Brunt allowed the photo machine to document his exit disguised as Lila.
Ned and Chuck arrive at the dam and capture Brunt.
Amelia pays Emerson for his services. Later, Emerson meets alone with Lila on a deserted country road. Lila thanks him and informs Emerson that Penny is in her car. She assures Emerson that Penny lives as normal a life as she can give the girl. Emerson figures she's lying and demands custody. He promises to get the cops to drop the kidnapping charge if she cooperates. Lila says she's broke and Emerson offers her his car. She gives him a kiss and admits she could always count on his big heart, and wonders if she was a fool for leaving him.
As Lila walks away, Emerson approaches the car, looks in… and finds a dummy. The car is disabled and Emerson realizes he's been tricked again. As Lila drives away, Emerson sees a happy Penny in the backseat and realizes that Lila loves their daughter too.
Back at the office, Emerson gets a letter confirming that his "Lil' Gumshoe" book will be published and is encouraged that Penny will one day find him.