"We need to find them, first." Still not entirely willing to believe that it's Loki, still holding on to that one in a billion chance that this could be someone else pulling the strings. And if that's the case, if Cho walks away and allows a friend and an innocent girl to be hurt, she'll never forgive herself.

The walls are unreliable, but the air, she thinks, might be safe. So she creates weather on a very small scale, spreading a layer of warmth six inches over the ground, even as ice crystals spread through her hair and over her clothing, and she uses the fog it causes to tell where it is and isn't safe to walk.

There are walls that appear to be solid, but are not. Sif is still the one going first, but Cho directs her, and hopefully by now she has earned the trust to not be questioned.