Thor was there in seconds. The man did not sleep this night. No. He paced around the home inside and out, thinking and grinding his brain upon what this could be. All of the day previous since seeing his own mother's ghost he had be hunting for the source. The god was both tired and full of energy even as the day wore into night and night into the morning of the following sun. He wouldn't let Loki see their mother that way. He did not think Loki fragile by any means but he knew how much their mother had meant to Loki, far more than she had to Thor if one had to gauge such a thing. It was unfair, really, but Thor conceded that Loki just had a certain relationship with Frigga he had never obtained.
So he worried and fought so Loki would not have to suffer seeing her this way, torn to pieces and shedding skin like a snake and oozing some sort of smoke that Thor was sure might suffocate them all with fear alone. Furthermore, he would not let Katherine see her. He could not. She did not need to see the woman in such a fashion. To ruin all of her ideals and dreams of what her grandmother had been, how beautiful and graceful and strong she had been.
The emotions within his chest sometimes made Thor want to fall to his knees.
The scream from Katherine upstairs brought him promptly. His feet carried him up two at a time. Thump. Thump. Heavy booted feet on the floor, the hall. Thor reached out for Katherine with a strong hand and pulled her near to his chest, strong left arm supporting her while the right thrust forward with Mjolnir. There was a bright flash of lightning in the room, then silence and stillness as it faded. Thor sighed.