Cedric was silent for a long moment before nodding. "Yeah, let's go." 

 There were two reasons why he didn't decide to retreat to the safety of the Sanctuary: 1) He didn't want to leave his brother and 2) He didn't want to go through that suffocating tunnel again. Plus, he probably wouldn't be allowed to live if his brother left anyways, so there was really no point. 
 
 "But are you really sure about this, Colin?" he asked. He looked at him with a serious glint in his blue eyes. "Even if there are other survivors out there, what makes you think that they'd accept us so easily? They'd probably prefer to just shoot us on sight and not bother with trying to befriend us."