SWEENEY TODD, DEMON BARBER OF FLEET STREET | Stephen Sondheim's 1979 cannibalistic "musical thriller" proved that a composer-lyricist can tell any damn story he likes. In Hugh Wheeler's book, a barber's revenge and a meat-pie maker's opportunism expose the power of hate over love. Alternately folk opera, revenge tragedy, neo-Brechtian protest, and penny-dreadful melodrama, this piece is above all an ensemble effort. And that's the secret to the success of this scorching Porchlight Music Theatre Chicago production. Never have the denizens of Fleet Street seemed so appropriately zombielike, their decomposition demanding a demon barber to finish them off. Michael Aaron Lindner's seething Sweeney all but sprays magma across the stage. And Rebecca Finnegan's pie-baking Mrs. Lovett--a serious harpy--is admirably straight-faced, too busy being ridiculous to know she is. L. Walter Stearns's cast seize every moment in their superb caricatures, the perfect illustrations for Sondheim's scathing score. Through 11/7: Fri-Sat 8 PM, Sun 3 PM. Theatre Building Chicago, 1225 W. Belmont, 773-327-5252. $25-$27.