Terminator Genisys Ending: What Does It Really Mean?

What Happened To Sarah In 1973?

The timeline splits in 1973, when the T-1000 is sent back to kill Sarah as a child. It finds and murders her family at their lake-house, but before it can complete its mission is apprehend by a young Pops, who takes Sarah away. It's a pivotal moment, the key to all the later time-meddling, and yet the film doesn't spend much time explaining what's going on. The T-1000 is clearly sent by Skynet, the latest in a long line of attempts to wipe out the Connors. And, as it's the start of the timeline fracture, it's likely instigated by Matt Smith's Skynet after he turns John into a machine (probably sent assuming that the T-800 sent to 1984 would be defeated by Kyle Reese). It is thus both an extension of the original approach and a way to build a new timeline with a new Judgement Day. It's never stated in the film, but the producers have confirmed that the T-1000 from 1973 is the same one that we see in 1984, played by Byung-hun Lee. This means that in the eleven years between attacks, Sarah and Pops have been perpetually on the run, trying to find a way to defeat him. That explains why they had the time to set up all those acid barrels.