mike stern: they did.had a pool, sometimes 10, 12 kids, just splashing around for hours and hours. it was a good time. keith morrison (voiceover): until it wasn't. in 2013, when sarah was just 15 years old, her mom carla died after a long struggle with cancer. keith morrison: what was it like when her mother died? sarah was at our house that night. and all i remember is sarah-- just hearing her sobbing downstairs. i didn't know what to do. did you know what had happened? yeah. yeah. just hard, and it was sad. keith morrison (voiceover): but sarah managed. instead of turning into her grief, she reached out, got even closer to her grandmother. and her dog buddy became her constant companion. she loved buddy so much. she really did. keith morrison (voiceover): she grew closer, too, to classmates at neptune high school. her friend, liam, his twin, seamus, preston taylor. preston took her to the junior prom-- just friends. she also made a different kind of friend, one you wouldn't necessarily expect. after carl