You'd need a giant ferris wheel o' time travel. You could in theory beat the light to where it was heading and again in theory arrive back in time by beating the light to it's intended destination. Here's where I try to explain complicated things. Two-way time travel is going to a point in time and then returning to the point you came from. So the journey never happened and granny didn't die after all.
Causality is a hypothetical law that says causes always precede effects.
Feynman pointed out that this is exactly equivalent to a single electron bouncing off a gamma ray and traveling backward in time before bouncing off a second gamma ray and continuing it's path into the future. Many geniuses, in my opinion, have come up with their theories of two-way time travel.