Chuck ends up hanging over the Alps, of course -- you knew that was coming the second Riggle said "gondola" a million times -- and is denied help several times. First because it's like the Ultimate Test and thus lights up Riggle's eyes something fierce because maybe they'll both die; then because it's literally as close to PFOD as you can get; then because this is the perfect example of a situation where Sarah, his rock [got it] can't help him: "Tell yourself you don't need her, and give in to the fear!"
Ah, but Chuck knows damned well he needs Sarah. Specifically that he loves her, which means needing her in a way that is both less and more scary than hanging out of a gondola by your fingertips while ten sexy tons of Rob Riggle fights multiple Eurobaddies inches from your nose. "I'd rather love Sarah than have the Intersect," Chuck grunts, somehow both completely getting and completely missing the point at the same time, but either way he's not flashing and Riggle's not budging, and it's a perfect hit of that old-school toughness I was whining about a second ago.
"CIA didn't send me out here to affirm your love, Bartowski. You need the Intersect up and running. Now, get that rock off your chest and be a real spy." Beat. "Like me!" Beat, and then Riggle gets shot through the chest and falls to his death with one final, gorgeously weird "Did I just get... Shot? I certainly did!" The Belgian pulls Chuck back into the gondola, and answers his phone to tell Walker that she won't be looking for them, or contact them further, or else Chuck is dead.
Back home, Sarah calls the General from Castle, but between acts the Belgian has disappeared from Gstaad on a private jet that has since apparently landed nowhere at all. The General promises that she's got word out everywhere and it's all very Code Red and please calm down, and puts Casey on the new mission. "Sarah, he's out there. We'll find him. But until there's intel, go home and get some rest. You'll be informed of any developments." Sarah swears she's not leaving Castle, and the General orders her home. Casey tries to comfort her -- "Bartowski's smart. Intersect or no, he'll be fine" but Sarah knows damn well he got into this mess: Sarah telling him over and over not to get into this mess.