The worst happens some ten minutes in to The Show Must Go On, an engaging, low-key doc on The Flying Wallendas, the wire-walking circus family that has been defying gravity with exquisite balance foe eight generations now. Their signature feat, created by now-gone patriarch Karl Wallenda, is a seven-person tightrope pyramid that stacks Wallenda atop a pole atop other Wallendas also atop poles atop a base of Wallendas walking the wire. It’s thrilling, a feat of daring and coordination and last-century discipline. It looks so difficult that viewers might not be surprise to learn that it collapsed, once, in Detroit in 1962, sending Wallendas to the dusty circus ring below—and killing two. (This is glimpsed here in a series of upsetting stills.) But Wallendas gotta fly, and Karl must have given a speech for the ages, because here they are, 50 years and several generations later, still pyramiding across wires without a net. “We may as well just do it five feet off the ground if we’re going to use a net,” scoffs Tino, a sixth generation performer and the current Wallenda leader. The move, running just an hour, follows Tino and family on a short tour of fairs; despite occasional runs with the Big Apple Circus, life for these likable, normal-seeming folks isn’t what it was for their predecessors. What drama there is here concerns the breaking-in of a non-Wallenda wire-walker, one whose nerves could send the pyramid crashing. Also, Tino suffers a crisis of confidence: “I feel like Superman one show, Tinkerbell the next,” he says. But then he thinks about the grace that matters as much to the act as strength and adds, “Actually, Tinkerbell would be pretty good.” Director Paula Froehle makes these high-stakes lives seem amusingly ordinary but no less fascinating.