After an enraged drug addict pulls a gun on Dr. Chen and other staff members, a fed-up Dr. Carter leads a divisive walkout when his request for metal detectors is delayed -- thereby endangering the lives of new patients. Elsewhere, Dr. Lewis counsels an exhausted elderly woman whose adult son is dying from Huntington's disease -- the same affliction that killed her husband. In addition, Dr. Pratt tries to safeguard his developmentally disabled brother and comforts Chen after her brush with death; Dr. Kovac treats an HIV-infected boy whose parents arouse his curiosity; and Abby's brother gets an eyeful when he visits the hospital.