Gerard followed after, lifting his wand again. When the other mice had followed the first, he'd become a bit more alert. Usually when mice ran together, they were running from something, not to.
It was a bit dark as they got closer to the thing, and Gerard extended his wand. "Lumos." The object was still a bit difficult to make out in the light of his wand, but it didn't seem to be immediately threatening. Still, he knew better than to get much closer to it without knowing exactly what it was and what it might be capable of.