Molly's abilities apparently made her very sensitive to supernatural energies. Jo could feel the wards that were at Harry's house. She didn't know exactly what they were, but she felt a wall of power up ahead. For just a minute, Molly's wizard's Sight opened up and everything pulsed out at her in a blinding array of colors.
Jo's head felt like it might split open until she heard Dean's voice. She looked up at him and got a glimpse of something that was almost a mini-soulgaze. There was Dean's face, only with a harder set to it, ready for anything. He held a silver sword in his hands. There was the slightest lurking shadow of the Dean she'd seen that had said yes to Alastair in hell.
"Ouch," Jo said loudly, and then forced her eyes to close and shook her head.
She took a few deep breaths and then slowly opened her eyes, the memory of how everything had looked now burned into her brain.
Molly's fingers had at least returned to normal and were no longer glowing.
"Okay. This stopped being fun about two hours ago," she said with a slightly shaky voice and a forced smile.
She approached Harry's door and knocked, ready to stop Dean from trying to go inside without an invitation. She understood enough to know that whatever she'd seen protecting the house would kill them both where they stood if they tried to enter without a member of the household allowing them in.