Sam is an aimless 33-year-old in Silver Lake, Los Angeles, interested in conspiracy theories and hidden messages in popular culture and uninterested in paying his overdue rent. The public is warned to "Beware the Dog Killer" who is murdering pets. Sam meets his new neighbor, Sarah, who despite having caught him spying on her, invites him over. The two get high and watch How to Marry a Millionaire, but when her roommates interrupt as they begin to kiss, Sarah suggests Sam leave and they hang out the next day.In the morning, Sam discovers Sarah and her roommates have moved out overnight, and becomes obsessed with learning what happened. Noticing a strange symbol painted on the apartment's wall, Sam trails a woman from the apartment to a series of elite Hollywood parties, encountering the pop band "Jesus and the Brides of Dracula" and a performance artist working for a prostitution ring of struggling actresses. All seem connected, but Sam struggles to find any meaningful pattern.At his apartment, Sam sees a news report detailing the discovery of billionaire Jefferson Sevence, burned to death in a car with three women. Sam recognizes Sarah's hat at the scene, and a small dog similar to Sarah's found dead.Sam contacts the author of Under the Silver Lake, an underground comic about neighborhood urban legends. He tells Sam that Sarah's disappearance, the Dog Killer, the Owl's Kiss - a naked woman in an owl mask who seduces and kills people in their sleep - and messages in pop culture are part of the same conspiracy and has installed security cameras throughout his house. Later, the police find the author dead in an apparent suicide. Sam enters the house and reviews the security footage, discovering the author was killed by a woman dressed as the Owl's Kiss.Following clues hidden in Jesus and the Brides of Dracula songs, Sam meets the "Homeless King", who brings him to a bunker underneath Griffith Park leading into a supermarket. With the help of the performance artist and her friends, Sam meets "the Songwriter", a fabulously wealthy old man who claims to have written most of history's popular songs. When the Songwriter tries to shoot him, Sam bludgeons him to death with a guitar that purportedly belonged to Sam's musical idol, Kurt Cobain.At a party in the Hollywood Hills, Sam meets Jefferson Sevence's daughter Millicent, also running into his now-famous ex-girlfriend and her new boyfriend. Millicent convinces Sam to go swimming in the Silver Lake Reservoir. She gives him a bracelet - identical to Sarah's - that belonged to her father, and is shot dead by unseen assailants and sinks to the bottom of the lake, mirroring a pose from Sam's favorite issue of Playboy.Sam manages to escape, and combines the bracelet, the author's cereal box prize, and a Legend of Zelda map from the first issue of Nintendo Power to reveal a location absent from web mapping where he finds a man and three women in a small hut. As Sam holds them at gunpoint, the man reveals the truth: throughout history, wealthy men such as himself chose to lock themselves in underground bunkers similar to the one Sam discovered, much like Egyptian Pharaohs, in order for their souls to "ascend" accompanied by three wives. Sarah and her roommates were Sevence's wives, and their deaths were faked. Their bunker has been sealed, but they can still be contacted via video-telephony. Sam speaks with Sarah, who confirms that she entered the bunker willingly. At peace with her fate, she and Sam share an emotional farewell.Sam begins to pass out as the Homeless King arrives to capture him, angered by finding dog biscuits in his pocket. When Sam tells him that he did not actually have a dog and kept biscuits only as memory of his painful breakup and knowledge that he would never see his girlfriend's dog again, the Homeless King lets him go. Returning home, Sam spends the night with a neighbor whose parrot repeats incomprehensible words. From the balcony, Sam watches as his landlord and a police officer enter his apartment to evict him. They notice one of his walls has been painted with the strange symbol seen earlier, which Sam now knows to be a message from the conspiracy to "stay quiet".