Director Mitch Massaro calls this play “a dark romantic comedy about the apocalypse,” which is not untoward given the creative background of author Peter Sinn Nachtrieb. The San Francisco-based writer’s works have been staged at (or commissioned by) important regional theaters, including D.C.’s Woolly Mammoth, Seattle Rep, Actors Theatre of Louisville, South Coast Rep and American Conservatory Theater. Boom — Theatre Communications Group’s most-produced play during the 2009-10 season — explores the influence of fate versus randomness, as a grad student’s online personal ad gains him an evening of no-strings-attached sex, interrupted by a catastrophic planetary event. Yes, it’s a comedy, and it seems to be a smart selection for the premiere of Actors Bridge Ensemble’s ambitious and emerging Sideshow Ensemble contingent. True to the group’s work ethic, performers and techies trade off roles in a collaborative spirit that worked successfully in their previous mounting, The Flu Season. Massaro stages the proceedings while Michael Redman handles set design; veteran director Jessika Malone designs the lighting, and designer J.P. Schuffman does the acting, supported by Hayley Rose and Amanda Meador. The Sideshow folks also recently announced a new website — sideshowfringe.com — and are still considering artist applications for their Aug. 2-5 Sideshow Fringe Festival.