The following version of this book was used to create the guide: Powers, Kevin. A Line in the Sand. Little, Brown and Company, 2023.

Kevin Powers's novel A Line in the Sand is written from the third person point of view, in the past tense, and set primarily in Norfolk, Virginia. The novel largely adheres to a conventional narrative plot line. The following summary abides by a similarly linear formal structure.

Four years after Arman Bajalan's wife and son were killed in a massacre in Mosul, Iraq, Arman relocated to the United States. Having worked as an interpreter for the United States military, he was granted a special immigrant visa after his life was threatened. Ever since, Arman had been living in Norfolk, Virginia. He was working for Mr. Peters, the owner and operator of the Sea Breeze Motel. Although the work was fundamentally different than his past career, it gave Arman the chance to detach from his past. He had also developed a close relationship with Mr. Peters, who he felt he could trust.

In order to quell his ongoing sorrow and grief, Arman tried to numb himself with rituals and routines. One of these was his morning swim at Ocean View Beach, located not far from the motel. Because the bus was late, Arman arrived at the beach later than usual one morning. Everything felt off to Arman and he could not help feeling suspicious of the men he encountered in the beach bathroom. Not long after emerging from the water, Arman then discovered a dead body on the sand.

Detectives Catherine Wheel and Lamar Adams were assigned to the John Doe case. They reported to Ocean View after Arman placed his call to the police. The dead body had no identification. When the detectives questioned Arman, he was unsure if he should trust him as his experiences with Americans in Iraq had complicated his sense of truth and trustworthiness.

Meanwhile, Sally Ewell was struggling with her own sorrow and grief. Although some time had passed since her brother Stevie was killed in combat overseas, she had yet to heal from her loss. She fell into a depression, attempted suicide, broke up with her boyfriend, and became reliant on alcohol. As a result, her work with the Virginian-Pilot had begun to suffer. Although her editor Matt knew that she had been sloppy of late, he agreed to let her pursue her investigation of Decision Tree International, a private military contracting corporation run by Trevor Graves. Sally had little evidence to prove her theory, but she suspected Graves of illicit overseas activities.

Over time, Sally's case began to overlap with Catherine, Lamar, and Arman's case. After Sally connected with her ex, a congressional aide named Trey West, Catherine received her contact information from Matt. Before long, Catherine, Lamar, Arman, Sally, and Trey were working together. Sally shared a thumb drive with them that an anonymous individual, who the detectives suspected was John Doe, had sent her at the office. Then Arman shared footage he had taken of the university massacre. The characters quickly realized that their investigations were two sides of the same mystery.

Trey disappeared, taking the laptop and thumb drive with him. Although Sally had believed him to be trustworthy, Trey was involved with Graves and his men, Harris, Dempsey, Jimmy, and Chris. These men were not only responsible for the university massacre, but for John Doe's recent murder. Catherine, Lamar, Arman, and Sally were beginning to understand Graves's desperation to cover his corporation's involvement in the Mosul massacre so as to protect his pending multibillion-dollar contract with the government.

Over the course of the following days, Graves's men become so desperate to reap the monetary rewards of their work that they stormed the motel and killed Mr. Peters, murdered Harris, shot Trey, invaded Sally's childhood home and shot her father, and stabbed Lamar to death. Because Chris was the last man alive after this sequence of violent incidents, he believed he deserved his payout immediately. Graves was not eager to let him go so easily. He still feared that the thumb drive, laptop, and files might leak and ruin his prospects of securing the contract.

Determined to avenge Arman's family's death and Lamar's death, Catherine snuck into a private Decision Tree event. She and Chris ended up in a scuffle, in which Chris stabbed Catherine and Catherine killed Chris.

Although she solved the case, because of her sloppiness with the evidence, Catherine was forced to retire from the force. She, Sally, and Arman maintained their friendships thereafter. Catherine had been a source of encouragement for both Sally and Arman.