In the future, Em lives a life of torment. Imprisoned and tortured every day as endless war rages outside, her only chance to set things right is to go back in time alongside her best friend, Finn, and kill the one who built the time machine and caused the future to end. Nothing else has worked, leaving death as the only option, and with the sadistic doctor catching onto her, this is her final chance to save the future.
In the past, Marina knows nothing of this—she's happy to see her James again, even if she doesn't always understand his theories, and finds Finn an annoyance at best. Marina is hopeful that James reciprocates her feelings, but when his brother is suddenly killed under suspicious circumstances, all her hopes for the future collapse into the desire to keep him safe at any cost.
Em and Marina are on a collision course, as they're both the same person at different points in time—and only one future can survive.
This book contains examples of:
- Awful Truth: For Marina, learning that James is the cause of the bad future. For James, learning that his future self became a monster and killed his own brother, who he built the time machine to save.
- Bad Future: Em is trapped in one that James created.
- Big Bad: The doctor, who is future James.
- Can't Kill You, Still Need You: The doctor keeps Em and Finn alive because they know the whereabouts of top secret documents. It's later revealed that they burned them ages ago and he uses it as an excuse to keep them alive, wanting them to truly believe he's made a better world.
- Childhood Friends: Marina and James met as children. As teenagers it blossoms from friendship into romance.
- Driven to Suicide: Ultimately, James kills himself to avoid becoming a monster.
- Fallen Hero: James started as a scientific prodigy and had a brilliant mind but eventually became a totalitarian dictator.
- Future Badass: Em and Finn are much more war-torn and athletic than their past selves.
- Future Me Scares Me: This plays a huge part in the book. Em, future Marina, scares her past self, but this trope really comes into play when James learns his future self is the doctor.
- I Call It "Vera": The time machine is named Cassandra.
- Never the Selves Shall Meet: It's claimed that if past selves see their future selves, both will be erased from existence. It's a lie intended to stall them.
- Promotion to Parent: James' older brother, Nate, took over raising him after their parents died.
- Ripple Effect-Proof Memory: Averted. The only reason Em knows anything about her past attempts is a note.
- Save This Person, Save the World: Inverted. To save the world, James must be killed.
- Set Right What Once Went Wrong: This is Em's mission, something she's failed at 14 times.
- Star-Crossed Lovers: Marina and James, since Em has to kill him.
- Temporal Mutability: It's "Temporal Balancing Act" mixed with Overwriting the Timeline. Change can happen. Lives can be saved or taken, but a new timeline will be created from the events.
- Well-Intentioned Extremist: James wanted to use time travel to save people from dying, but he ended up using it to kill people who became a threat to him, including his own brother, and turned everything into a police state.
- Wham Line: "James," I say, calm at last. "You killed your brother."
- With Great Power Comes Great Insanity: This is what happened to future James in a nutshell.