Lyric Opera of Chicago stagehands found themselves in the middle of some real-life drama just outside their doors last month when they came to the aid of a tourist being pummeled in broad daylight. Police say Mark Ball, 50, allegedly began beating a 27-year-old Boston man — for no apparent reason — near 20 W. Wacker about 2:30 p.m. on May 28. For Robert Hartge, a laid-back day — the last of the season at the Lyric — was suddenly turned upside down in an instant. Standing inside the opera’s glass doors on Wacker Drive with other stagehands, Hartge noticed...