The following version of the novel was used to create this study guide: Ware, Ruth. Zero Days. Gallery/Scout Press, June 20, 2023. Kindle.

In the thriller Zero Days by Ruth Ware, Jacintha “Jack” Cross’s life ended when she walked into the home that she shared with her husband Gabriel “Gabe” Medway to find he had been murdered. Believing she had somehow become the main suspect in her husband’s death, Jack walked away from the police station during a break in questioning. She went on the run determined to find out who had really killed her husband and why.

Jack and Gabe owned a freelance penetration or “pen” testing company. One night Jack returned home from a job to discover that Gabe had been savagely murdered. When she called the police, Jack was questioned by them repeatedly about the timeline of her discovery, including an unaccounted-for block of time when Jack sat on the couch in shock before calling the police.

As Jack sat in the police station, she received an email from Sunsmile Insurance indicating that a one-million-dollar life insurance policy was in place for her and her husband. Jack had not taken out a life insurance policy and did not believe that her husband would have done so without telling her. Jack realized that the police would see the insurance policy as a motive. Jack walked out of the police station because she sensed that the police already suspected her without even knowing about the policy. The policy will only add to her being a suspect.

On the run, Jack reached out to Gabe’s best friend, Cole Garrick, for help. He helped her by getting her a burner phone so she could communicate with her sister, Helena “Hel” Wick, without alerting the police to her whereabouts. Cole also gave Jack permission to stay in an isolated cottage owned by his girlfriend. During Jack’s first conversation with her sister by text, she noticed it was strange that her sister incorporated emojis into the text.

When Jack arrived at the cottage, she discovered the electricity was not working. She texted Cole, but the battery on her phone died before she received a response. That night, Jack was frightened when she heard a car motor approaching. It turned out it was Cole coming to check the electricity. He cooked dinner for Jack and spent the night because he had too much to drink to drive. He tried to convince her to turn herself in, arguing that it would be for her safety. He feared the people who had killed Gabe would try to hurt her. Jack refused and insisted she was going to find Gabe’s murderer. Jack was awakened that night by the sound of a police radio. It appeared Cole had led the police to her. Jack managed to escape.

Jack texted Hel with her plan to go to Sunsmile Insurance and hack into their computer system. She intended to find out who had really applied for the insurance policy. Jack used her pen-testing skills to access a computer terminal at the company and look at Gabe’s application. Everything looked legitimate, except Gabe had given them a phone number that was unfamiliar to her. When Jack listened to the recording of a phone call between the company and the man who had signed up for the policy, Jack recognized that the woman was talking to Cole.

As Jack prepared to leave the office, she noticed a large police presence in the lobby. Someone had alerted the police that she would be there. Jack knew her sister had not turned her in and that was the only person who knew where she was going. Jack managed to escape by triggering a fire alarm and then blending into the crowd of people leaving the building.

Meanwhile, Jack had injured herself when she climbed over a wall to escape police in an earlier scare. The wound was still bleeding and was hurting more and more. Jack feared she had an infection that might lead to death if she did not receive medical attention soon. Regardless, she was intent on finding out who killed Gabe and why before she went to a hospital, a move she knew would result in her being put in police custody.

Jack confronted Cole on the phone. She told him that she knew he was the one who set up the insurance policy. Cole claimed he was trying to protect her. He finally explained that Gabe had found a vulnerability in an app and had asked Cole’s advice on what to do about it. He said that instead of reporting the vulnerability to the company, Gabe tried to sell it on the dark web. Instead of paying Gabe’s asking price, the people who wanted it killed Gabe and took it.

To obtain access to Gabe’s backup files, Jack paid a hacker on the dark web to transfer the information from Gabe’s phone to a burner phone. Jack was able to determine from Gabe’s files that the vulnerability he found was in an app that Cole had created. Gabe had mentioned the vulnerability to Cole. When Cole did nothing, Gabe planned to tell Cole’s superiors about the vulnerability that impacted their parental monitoring app.

Jack determined that Cole had been paid to include the vulnerability in the app. She first posted on Gabe’s social media pages information about the vulnerability. Next, she confronted Cole and live-streamed the confrontation. Cole admitted he had been paid to include a vulnerability in the app and that if he modified it, he would be killed. With his life on the line, Cole decided to leave the app alone and let the people who were paying him off kill Gabe to keep him quiet.

Jack had used Gabe’s phone to stream her interaction with Cole, a move that gave police her location. Since Jack was so sick as a result of her injury, Cole escaped his apartment building where she had confronted him before she was able to catch up with him. Jack was accosted by police in the lobby of the building. When Jack reached for Gabe’s phone, which she realized in retrospect was a mistake, one of the officers hit her hand, knocking it into her wounded side, causing her spleen to rupture.

Jack awakened in the hospital after surgery to repair the spleen. She had determined why Gabe had been killed and identified a person responsible. She had fulfilled her goal. However, she felt that she had nothing to live for without Gabe. An orderly, however, told Jack that she was pregnant. A year later, Jack was still working as a pen tester, but her baby, Gabby, was her priority.