all those factors put together, sarah stern did not leave. on (voiceover): cold comfort to sarah's father because that meant something much worse. ed kirschenbaum: mr. stern was down at those docks every day, walking the docks, walking the shoreline, just wouldn't give up hope. we walked along the banks. we circled the entire shark river basin, marshy areas, and watched the currents come in and out, stood on the sandbars and watched the tides come in. during low tides, you get out there and really see a lot. but then within a couple of hours, tides come up maybe six or seven feet. cold, windy. it's slippery along the banks. it's not easy work. no. keith morrison: frustrating. yeah. keith morrison: did you see him out there? i did. i did. what did you think? my heart broke for him. for a father to not know the whereabouts of his daughter was devastating. keith morrison (voiceover): and mike stern had no inkling of the sea change about to occur in the search for his missing daughter. coming up. it shifted from a missing person investigation into