At Tieh's joke, Roga stops looking around and steps towards Kara.  "Hi," he tells her, "I'm Roga Jain.  I was on the boat."  He stays out of her reach, just in case she doesn't remember him.  "I doubt you'd be joking about something like this.  However, something strange is definitely going on, and until we find out what it is, you're just going to have to trust us.  We can help you find familiar people, but right now we have to make sure no-one else loses their memory."