i've never seen anything like the fritzl case. >> in that sunless, airless space, elisabeth fritzl gave birth to seven children. her tormenter? her own father. >> translator: intelligent, a strategist, an almost perfect criminal of the worst kind. >> for more than two decades, josef fritzl fooled everyone who knew him. >> nobody, nobody on the street noticed anything at all. >> until a few months ago when his cellar disgorged its dark and unspeakable secret. >> you couldn't write this in a novel. >> fritzl's evil quickly became a worldwide story. how did he do what he did? and, most importantly, how could he? >> april 19th, saturday morning in a small austrian village 70 miles from vienna. at 7:00 a.m., a call comes in to 911. a teenage girl, kirsten fritzl, is seriously ill. an ambulance is sent to number 40 ybbestrasse, the home of josef fritzl. at the local hospital, it had been a quiet morning. that was about to change as a young patient is admitted with symptoms that confound doctors. >> translator: she was in a state between life and death. >> the young woman is unconscious and ha