2 Books
See allContains spoilers
There was a lot of confusion in the last hour due to audio decisions, albeit it was a fun sci-fi. Read this only after you have completed it.
The timeline diverges when the temporal one saves the kids when the Malaysian flight went missing. That creates two timelines.
First and regular timeline: The AI in Mars, Greta, is revealed to be the mastermind of everything, as she is an entity that used humans as crops so that aliens can harvest us. The Temporal 2 team dies, and humans come back to Earth for the new cycle of crops to begin.
Second and divergent timeline:
The Temporal 1 team saves humans by using a frequency that tells the aliens that the crops went bad, i.e., humans are not ready for harvesting, which prevents humans from vanishing and the Mars mission from happening. Then, the Temporal 2 team will live on Earth with the other humans.
It's a pretty open ending and would have been great if it concluded properly.