Mako thinks that mostly because of the dolls he saw, and because his skin is looking oddly... shiny, in a way that he's deeply unsettled by.

He keeps behind Carlos as they walk up, both to catch him if he happens to fall and also because, honestly, it's self-preservation to let someone else go first. If they are turning into dolls, something that should be impossible outside the Spirit World and probably inside it, too, Mako doesn't trust anything that this house could throw at them.

As soon as they reach the attic, though, Mako stops, focusing in on— "Are those... broken pieces? That can't be good." He shakes his head and goes to investigate them, kneeling down with awkwardly stiff joints to very gently pick one up.