During last night’s Late Show, Stephen Colbert set out to to interrupt his mentor Jon Stewart’s blissful retirement in order to find an explanation — any explanation — for Donald Trump’s success.

“How can we guess what will happen,” Colbert said, referring to this week’s Republican National Convention in Cleveland, “if we can’t begin to explain how we got here?”

Colbert then reappears in Stewart’s isolated retreat, and asks his old friend for some clarity.

Jon Stewart has been a bit of a hermit this election season, rarely appearing every now and then, including for a wide-ranging discussion with David Axelrod at the University of Chicago in which he took aim at the American political culture that created Donald Trump.

Last night, though, Stewart stepped back in to his old on-screen persona to give voice to the overwhelming reaction to Donald Trump’s political success: That guy?!

Photo and video: CBS/ Late Show with Stephen Colbert