Timewatch: Making sure history happens at the correct time, in the correct location.  Ever since Dr Leah Breen and her team invented the Time Machine, Timewatch has been stopping people from going back and changing everything.

As an agent of Timewtach, you are a particularly talented individual from some point in history who was recruited by a TimeWatch agent and given an easy choice: live a life of mediocrity and die right on schedule, or become an elite investigator with an extended life span who fixes problems in the true time stream. TimeWatch has trained you in history and chronal theory, has given you a time machine and a weapon, and has set you to guarding the history of humankind.

Time travel created innumerable threats to our existence, and if you do your job right, we’ll never hear about a single
one. If you do your job wrong, you may erase history as we know it. So try not to do that.

Parallel universes, alternate timelines and chornal paradoxes all threaten our very existence, including that of everyone who has ever existed, currently exists and will ever exist.

As you know, over 50% of Timewatch's staff is dedicated to making sure 2 people die at the right time and not earlier.  Adolf Hitler and Josef Stalin.  Somehow, someone slipped through and removed Hitler yet again.  As per normal, this has resulted in the destruction of most of the planet Earth in a global nuclear war, allowing the Ezeru aliens to invade Earth and inhabit it as a nuclear wasteland. 

We have traced the source of the disturbance to 1865 Munich, much earlier than we thought to place guards.  Go there and discover what happened this time.