The following version of the novel was used to create this study guide: Sager, Riley. The Last Time I Lied. Dutton, July 3, 2018. Kindle.

In the mystery/thriller The Last Time I Lied by Riley Sager, Emma Davis agrees to return to Camp Nightingale, where three of her cabin mates disappeared years before, hoping to make amends for what had happened. Francesca “Franny” Harris-White, the owner of the camp, encourages Emma to return as an instructor with the argument that Emma will finally be able to get closure. Emma sees spending time at the camp as an opportunity to investigate the girls’ disappearances on her own. When three more girls disappear from the camp, Emma is the main suspect in their disappearance.

Emma is surprised when Franny, the owner and director of the former Camp Nightingale, approaches her during Emma’s first art show. Emma's paintings look like three-dimensional forest scenes. Emma and one of her closest friends are the only ones who know that she always starts her work with paintings of Vivian, Natalie, and Allison. Then, Emma applies additional layers of paint, symbolically causing the girls to disappear into the forest again. Franny suggests that Emma should teach painting at the camp which Franny is opening for the first time in 15 years. The three girls in Emma's paintings were her cabin mates before they disappeared. Later, Vivian, Natalie, and Allison were declared dead.

Emma agree because she hopes to find something that will tell her what happened to her friends. Emma begins searching as soon as she is able. She finds a map that Vivian hid in the lining of her trunk as well as a picture of a woman with desperation in her eyes. The map leads Emma to Vivian’s diary. In it, Vivian hints at her search for a secret kept by Franny. The secret appears to have something to do with an asylum, the women who lived there, and Lake Midnight.

Meanwhile, Emma has been experiencing strange things ever since she returned to the camp. She notices a surveillance camera has been set up outside the cabin where she is staying. She wakes one morning to discover someone watching her from the window. One day three birds are intentionally trapped in her cabin. Another day the word “LIAR” is painted on the door of the cabin. Franny and her oldest son Theodore “Theo” Harris-White confront Emma and tell her that they had the camera installed because they knew she had been institutionalized for a mental illness after the girls went missing 15 years earlier. They believe the camera is a way of protecting Emma from herself.

The majority of the novel is set in the present, but Emma describes some incidents that happened 15 years ago. She describes how much she admired Vivian and wanted the older girl to like her. Emma also describes Vivian’s jealous and manipulative nature. Both girls had crushes on Theo. On the day that Vivian and the others disappeared, Emma believed she saw Vivian having sex with Theo in the shower. Angry at Vivian’s betrayal, Emma yelled at Vivian as she left Emma in the cabin alone that night. She hoped Vivian never came back. Those words haunted Emma. Emma also regretted blaming Theo for hurting the girls, an accusation that came also from her anger that Theo had chosen Vivian.

In the present, the story climaxes when Sasha, Krystal, and Miranda, the girls who are in Emma’s cabin, disappear. Emma is the main suspect in their disappearance until Emma takes matters into her own hands. She returns to a spot across the lake they had explored earlier and discovers the girls have been locked inside an old root cellar. They do not know who locked them inside.

When Theo surprises Emma by following her across the lake, she assumes that he is guilty and has come to hurt the girls. She instructs them to return to camp while she keeps Theo away from them. In her attempt to keep Theo from hurting her, Emma falls down a shaft into a cave. The cave opens into the lake. Emma believes she has been saved when she swims from the cave to the lake and finds Chet searching the lake in a motorboat.

Chet, however, admits he is not Emma’s savior. Instead, he is the mastermind behind the strange things that have been happening to her. He holds her responsible for the treatment his family received after she accused Theo of being responsible for the girls’ deaths. He takes her to a little-known cove in the lake where he intends to kill her. Emma recognizes the rooster weather vane sticking up through the water of the lake as the one she has seen in pictures of the asylum that was once on the property.

Chet intends to kill Emma, but he is stopped when Detective Flynn shoots and destroys the oar Chet was about to use to kill her. Emma falls out of the boat and down through the roof of the old asylum. As she swims out toward the surface, she sees two skulls and a necklace Vivian once wore.

Months later, Emma is notified that the bones she found belonged to Natalie and Allison. It appeared they had been hit in the head and weighted down with blocks to ensure they would drown. None of the remains belonged to Vivian. Later that day, at another art show, Emma is approached by a woman that she realizes is Vivian. Vivian indicates that she planned the murders of Natalie and Allison because they had dared her beloved sister Katherine to try to walk on an ice-covered reservoir. Katherine had fallen through the ice and drowned. Natalie and Allison did nothing to help her.

Emma returns home that night and paints a picture of the modern-day Vivian which she sends to Detective Flynn, hoping Vivian will be caught and punished for her crimes.