To solve an overabundance of cod, temporal agents from a future Mars must travel to past Earth, take over the bodies of a pair of polar bears, seek out baby seals (the natural predator for cod), and return with them to the red planet where they hope they will grow up, breed, and resolve the cod problem. All without damaging Earth’s endangered populations of both polar bears and seals.
What could possibly go wrong?
Well, managing ecological niches is tricky stuff in the best of circumstances. Add in a bumbling agent, unforeseen consequences, and a temporal ripple, and the future of Mars won’t be quite the way they left it.