Timeless has so far come up with a pretty good solution. Bad events as we know them - last week the Hindenburg disaster, tonight the Lincoln assassination - are just slightly changed. They're not stopped, but the surrounding circumstances of the event are slightly changed - because, in both cases, so far, the time-travelers are in action on the scene.
The result is that the world in the future - our world, as we know it - stays the same as far as major events. But little parts of it change, specifically the family and now the love-life of one of our major characters, Lucy. At least, so far.
Fortunately for Lucy, we the audience, and the narrative, there's a character at time-travel central who's able to map out for Lucy exactly why the little changes in the past led to the big changes in her life. This gives Lucy and us a better idea of what's going on.
But still unclear is the villain's agenda, and why he - Flynn - is so bent on making catastrophes of the past even worse. I suspect, am hoping, that the reason has some personal connection to Lucy, known or unknown by Flynn, because that will an add even bigger dollop of tension to the contrary forces that are pushing her to change history, presumably for the better, but with who knows what effect on her personal life, and leaving the past as it was and she knows it and her life in the future to be.
A nice kettle of fast-moving, subtly visible fish in which to situate time-travel stories.
See also Timeless 1.1: Threading the Needle
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