This particular performance of Puccini’s La Boheme, recorded in April as part of the transmitted-live-to-theaters worldwide HD live opera simulcast, has a behind-the-scenes story as dramatic as anything on stage. This opera’s staging by Franco Zefferelli is one of the most popular and most-repeated productions in the Met canon – but on this particular occasion, there were unforeseen problems. The leading lady, Romanian soprano Anita Hartig, came down with a bad case of the flu – and informed the show’s producers of that fact in the early morning hours the day of the scheduled live simulcast. Rather than cancel the New York Metropolitan Opera matinee, and the global simulcast, the producers went with an unprecedented solution and found an instant replacement: Latvian soprano Kristine Opolais, who had made her Met debut the previous night, starring as Cio-Cio-San in another Puccini masterpiece, Madame Butterfly. She knew the role of Mimi in La Boheme, having sung it in other productions, and embarked on an all-morning crash course to try and learn the staging, the timing, and to get a feel of her co-stars’ vocal and acting approaches. The performance you’ll see on TV tonight is the result: the first time in Met history that an actress performed two different starring roles on successive days. That electricity you’re watching, as Opolais sings with Vittorio Grigolo as Rodolfo and others, isn’t just coming from your TV set. It’s coming from the performers of this operatic high-wire act – and from the audience, too. Wait for the curtain call (pictured).  Check local listings.