Apparently, science isn't exactly perfect. Even when it's done by the likes of Winston and his genetically enhanced brain. It's just my rotten luck that when it does screw up, it leaves me separated from Earth entirely and completely unable to fulfill my duties as an Overwatch member. But where I end up really did need more heroes.
First I end up having to deal with a war between humans and robots, then I get involved in alien crises just as crazy. Hmph, good for them the cavalry dropped in!