Callie kept on running, her answer to his comment about doing their part being, "[b]But I don't even know what that part is!!! How can I even do that if I don't know?![/b]"

He clearly knew more than she did, and she knew she was going to be lost if he died.

Then he lets out a shocked 'No', and though Callie wanted to ask, now wasn't a good time. 

She gasped and screamed when something was thrown at them and she was shoved out of the way. Before she even knew it, the thing was standing between her and Merrill. She found herself sitting and trying to back further and further away from the creature still sitting. She couldn't help but let out scared whimpers as she backed away.

Of course, Merrill had gotten its attention and threw something at it. 

Callie watched in fear as Merrill fell, missing the taloned swipe. When he called her to do something, she saw another spark, this time it was red, and it seeped into her fingers. She could feel fire in her hands, and she pointed her hands at the creature, sending flames it's way, and after the fire, came a blast of radiating light from her right hand. She desperately hoped that this would be enough to get rid of the creature.