he, of all people, should not just up and vanish. >> it didn't make sense to me. and so i just kept, no, it can't be. it can't be. i just kept hoping. i did everything i could. >> reporter: but even as she ran down leads herself, it seemed to tara that lisa, her sister-in-law, gavin's wife, wasn't searching. >> so he disappeared, and you couldn't give up on the possibility he was out there somewhere, and lisa could. and i wondered whether there were ever sort of dark nights to your soul where you thought i wonder if she had something to do with this. >> it crossed our minds all the time. it just did. i mean, did i think that she could ever be the one responsible, the physical? no. but somehow it kept playing back, why won't you search. why?