Em and Finn are being held captive in a military facility run by their former friend James. Em uses a spoon to dig around the drain in her cell. She finds a piece of paper written in her handwriting telling her "you have to kill him". One night Connor, a guard at the facility, helps Em and Finn escape. They head to the control room for Cassandra, the time travel machine built by James. Em and Finn travel back four years to January 4th. Marina, Em's past self, has been waiting for James and his brother Congressman Nate to get back from Connecticut. After they are back home Nate asks Marina to keep an eye on James. He asks her to look out for anything out of the ordinary. Marina agrees but doesn't understand why. Not to far away Em and Finn appear where the military facility will be. They convince a younger version of Connor, the guard who helped them escape in the future, they aren't crazy and the future needs to be changed. Connor helps get Em and Finn to where the banquet Nate is speaking at is taking place. When they get ready to find and kill James shots ring out as Nate has been shot. Nate is taken to the hospital and James rides with him. Finn and Marina head to the hospital to be with James. When James wants to be alone he heads outside and Em attempts to kill him. Everyone regroups as Finn, James, and Marina head to Finn's house since James and Marina's are swarmed with reporters. Em and Finn follow them and Em has a another chance to take out James, but she can't do it. Finn, James, and Marina head back to the hospital the next morning where Nate briefly regains consciousness. He uses sign language to tell Marina they should head to Connecticut to find answers about why he was shot. In Connecticut they find evidence of the government experimenting in time travel. They also find evidence the government is also interested in James. As they leave the house James gets the news that Nate has died. Em and Finn decide that even though James is at his weakest now, this is the best time to kill him. They are hopeful with the death of James the horrible future they come from will be prevented.
I really enjoyed this book. It was a good time travel book that didn't confuse you when the future Em and Finn came back to the past to try and kill James. The ending played out differently in my mind, but I liked the way the story ended.