Fired: A Young-Adult sci-fi thriller

Normally when you are eighteen year-old,you are a casual teenager with casual problems, but Sam here isnt the same. He has the weight of the world upon his shoulders! Ronald,with a beaten-up past, makes up his mind to destroy the world and make others suffer like they made him. The only thing getting in his way is Sam, with his time-travelling capabilites. Will Sam be able to stop Ronald from making the vaccine? Or will it be too late? But its never actually too late and when everything is lost, one thing remains....hope. But will that be enough for Sam to save everyone,he who has lost everything.