Helena had promised both of her parents, along with several others, that she wouldn't leave the castle. And what had she done? Promptly left the castle. The walls seemed to be closing in on her. Even Rabastan had left the castle to go and get something he'd forgot. Helena had followed him to the door and seen him out. Once he was past the wards, Helena had gone out too. She was just going to sit on the steps, let the wards keep her safe, and the door to her back so it was close if something happened.
After just a few minutes, Helena saw someone moving in the distance, just past the wards behind a few trees. It was the same general direction Rabastan had gone in. "Silly Rabbit, did you forget something here too?" She'd gone to the wards to meet him, stepping just a few feet too far. She didn't notice as she passed the wards, but she did notice as the face that she thought had been Rabastan's turned into someone else's. Someone she didn't recognize.
Helena had turned to run back to the castle, back into the wards, but the spell hit her from behind, pain racked through her body. Before long, the pain subsided and she was suddenly in the caves. She was deposited onto the floor in a heap before chains were secured onto her arms. Once the cave had quieted, Helena was sitting with her legs pulled to her chest and she was crying softly. Her parents would kill her if these Death Eaters didn't.