the musical. one thing is undeniable. the flying actors were engaged in death defying feats. what was at stake wasn t just artistry, but the safety of the actors. chris tierney fell 30 feet from éhd stage. broke three vertebrae, four ribs, my skull, scapula and elbow. reporter: you got pretty good stars out of that, i hear. yo! yeah, baby. reporter: we are going backstage. the humbled rock stars say they now appreciate just how much they had to learn. people coming through the doors have to have our best shot at this. and we ll see if our best shot is, is good enough. reporter: cynthia mcfadden, abc news, new york. that is pretty cool. pretty humble, too. you re a big u2 fan. yes. ofofofofofofofofofofofofofofofof