Sym learns from Victor and Manfred that the world is hollow. Sounds a bit suspect, right? Like the whole "the world is flat" thing?
The hollow earth theory is the work of a real dude named Jon Cleeves Symmes. He lived 140 years ago, which is presumably back when people thought the earth was hollow.
Symmes's Hole, as its called, is the object of Victor's obsession, and after fifteen years of looking, he thinks he's found it. This seems plausible to Sym, who thinks Victor is a genius.
Manfred, who is a film director, is on the trip to film Victor's journey to find Symmes's Hole—that's how they know each other. Also, it seems they've been planning this for a while.
Sym describes Symmes's Hole as a portal that leads to an underground labyrinth. Oh sure, sounds legit.
Victor tells Sym that explorers—including Titus (her Titus)—have been looking for the portal for years. It's just that no one has been successful. Yet.
Sym is having a hard time believing all this, but if Victor said it, it must be true… right?