Question: In the film *[Triangle](http://en.wikipedia.org/wiki/Triangle_%282009_British_film%29)*, we learn at the very end of the film,

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>  that the Jess we meet in the beginning already went through the loop (maybe even all of them). She remembers what happens on the liner, and she must remember that her main goal was to stop the entire crew from stepping onto the liner.
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When the moment comes when the crew wants to be "rescued" by the liner, why didn't she try to stop them? She hesitates, but doesn't act on it. Why?

Answer: 
After watching it again (I felt a lot like Jess, herself) I realised that she does not forget the events that took place until she is back on the Triangle. We can see her very sombre in the beginning of the film (when we have no explanation for it).

The reason she voluntarily goes back is because of what The Driver says about Tommy: "No point trying to safe the boy, nothing anybody could do's gonna bring him back." If you look very closely, you can see the slightest hint of her expression changing, because she has a new idea. It's not her goal anymore to safe herself, she wants to go through hell again (figuratively speaking) in order to prevent Tommy from dying in the next iteration.

However, when she steps on the Triangle, she falls asleep and forgets the previous events (until it's far too late, when she begins to very vaguely remember), as if they were dreams. After she wakes up we see her brightened up significantly. This is when her new plan to actually *get* on the ocean liner is forgotten and everything starts anew.
In the Liner, Jess is looking to stop the loop from happening, she wants to go back to her son. The son that she has forgotten she has ended up killing. When the loop starts all over again, she doesn't stop the people from setting sail because the shock of it all. 

While the whole thing looks like she is stuck in some kind of a time vortex, there is an alternate theory suggested in the link below at the end. I liked the batch approach to the explanation as well as it helps understand the 4 Jess' on the Liner:

[Triangle Movie Ending Explained](http://digestivepyrotechnics.blogspot.com/2014/12/triangle-explained-plot-holes-explained.html)