Sometimes described as a childhood version of ‘One Flew Over the Cuckoo’s Nest,’ Visitors is funny, mildly shocking, immersive, and tragic. At its outset, three children on the outside end up at the hospital after various small disasters, and blend in with an established population of kids that are… well, kids. Group therapy starts slow and builds to a crescendo. Free time is noisy and rambunctious. The girls have girl-talk at the picnic table outside. One of them quietly suffers through the whole thing and, eventually, finds she can’t contain it anymore.