Arcade Fire is in the midst of a multi-night run at Chicago’s UIC Pavilion with guest opener The National. During The National’s opening set last night, Arcade Fire bassist Richard Reed Perry emerged for “Afraid Of Everyone” and “Conversation #16.” A bit later in the show, Arcade Fire frontman Win Butler sat in on “Start A War.” The two bands toured together extensively in 2007. The group will return to Chicago’s UIC Pavilion tonight.