Whistler tried (and failed) to pinpoint the nexus of Rhiannon's destiny.

So he improvised.

"There's gonna be a moment, Rhi-Rhi." (Where the hell did that come from?) "Everyone has 'em. You can't get away from it. It's what comes after that's gonna decide who you're gonna be."

The Agent took a long drag of his cigarette before continuing. "It can be slippery. It'd help if you had someone ta hold onto, metaphorically."