Frau heard the voice through the fog of sleep and illness. There was no way he was going to be able to respond, but hopefully Kevin would try the door anyway. Mimsy would likely hear her owners voice and start barking. That would likely set Tolly off as well.

Thankfully Frau had been too exhausted after the green goo incident to lock the door behind him. Kevin would be able to walk right in, which was what Frau was hoping for. He could feel the heat pouring off of Teito's body, an extreme opposite to the iciness of his own.

Come on, Casper. Just come in.