Thanks to mental link over the force they unintentionally formed, Kylo unknowingly broadcasts to Rey every time Snoke brutalizes him. And she can't do anything to stop it

+at first she thinks he's intentially sending her these disturbing visions/feelings/etc to weaken and scare her but gradually realizes it's stuff he's experiencing firsthand and isnt sure what's worse
+she asks luke/leia for help
+eventual rescue?